I figured I would post the list of Trailer Train reporting marks since I found my article from RMC (August 1990) magazine listing:
ATTX - 75' all purpose flatcar (center and side tiedowns)
BTTX - 89' flatcar equipped with bi-level auto rack)
CTTX - 89' low level flatcar equiped with partially enclosed autorack
DTTX - 265' Five platform, articulated well-type COFC car capable of carrying double stack containers
ETTX 89'4" low level flacar equipped with totally enclosed tri-level autorack
FTTX 89'4" flatcar equipped with tie down devices for loading automobile or truck frames
GTTX 85' and 89' General American built flat car equipped with collapsable hitches and bridge plates for transportation of trailers
HTTX 60' Flatcar equipped with 38 heavy duty chains, snubbers and turnbuckles for carrying earthmoving equipment
ITTX 89'4" flatcar equipped with special fold away pedistals and 62 tie down winches with chains and bridge plates for carrying trailer tractors saddle back style.
JTTX 50 - 89'4" flatcar with misc devices applied for lessor special service
KTTX 89'4" "Twin-45" standard level flat car with fixed hitches at both ends for handling two 45' trailers back to back (over head loading only)
LTTX 89' Low level flatcar equipped with collapsible hitches and bridge plates.
MTTX 60-85' 60 foot flatcar with stake pockets for gen service or 85' flatcar with 16 stake pockets, 8 per side for tansporting long pipe.
NTTX 249' 5-unit articulated COFC car for transporting containers (spine car)
OTTX 60' Flat car equipped with 36 chains, with snubbers each secured to movable and retractable tie down winches in for longitudinal channels for tansporting agricultural equipment
PTTX 60' flat car equipped with bulkheads space 48'6" apart for transporting plywood and wallboard etc.
RTTX 89'4" "Twin-45/Tripple 28" standard level flatcar with fixed hitches on ends of car and retractable hitch at center of car. For handling two 45' or three 28' trailers (overhead loading)
STTX 89'4" "Twin-45" standard level flat car for handling two 45' trailers, equipped with sliding bridge plates for circus style loading
TTAX 89'4" Standard level flat carequipped with foldaway container pedistals and hitches for TOFC and/or COFC service.
TTBX 89'4" flat car equipped with bi-level auto rack, rack can be either open or shielded on the sides but does not have roof or doors.
TTCX 60' and 89' flat car equipped with container pedistals for COFC service.
TTDX 89'4" flatcar equipped with 16 tie down winches with chains and bridge plates for transporting military vehicles
TTEX 181'9" two unit TOFC car for hauling four 45' trailers or three 57' trailers (over head loading only)
TTFX 187'6" four platform TOFC car capable of carrying four 45-trailers
TTGX 89'4" flatcar equipped with totally enclosed bi-level auto racks
TTHX 60' 60-foot flat car equipped with 18 heavy duty chains anchored to stake picket astings
TTJX 68' 68-foot 100-ton flatcar equipped with 22 screw type tie-down devices and stake pockets.
TTKX 89' flatcar equipped with hinged "B" deck tri-level auto rack. Rack can be either open or shielded on the sides but doesn not have roof or end doors
TTLX 89' "Twin-45" low level flatcar specially equipped by particpant railroads with container pedistals or fixed hitches for assigned corridoor.
TTMX 68' 68-foot 100-ton flatcar equipped with stake pockets and lading strap anchors for general service
TTNX 89'4" flat car equipped with bi-level auto rack without end doors but with sides and roof panels.
TTPX 68' 68-foot flat car equipped with builheads spaced 62 feet apart and 34 transverse tied down anchors with chains used for transporting plywood etc.
TTRX 89'4" flatcar equipped with fixed tri-level rack without a hinged "B" deck. Rack can be either open or shielded on the sides but does not have roof or door.
TTSX 89'4" flat car equipped with coverless enclosed bi-level autorack.
TTUX 50'6" Single platform TOFC car with single axle trucks capable of carrying one trailer 40-48 foot and up to 102-inches wide w/ nose mounted refridge unit,over head loading only.
TTVX 89'4" Low level flatcar equipped with tri-level auto rack with shielded sides without end doors and without or without roofs
TTWX 89'4" Twin-45 standard level flat car equipped with fold away container pedistals and hitches for TOFC and/or COFC service.
TTX 50'-89' flatcar equipped with one or two hitches for TOFC service.
TTXZ 64' to 76' 100-ton bulkhead car equppied with center partition and winch type tie down system for carrying lumber products.
UTTX 256' Five platform articulated TOFC car capable of carrying one trailer per platforum 40-48 feet and up to 102 inches wide w/ front mounted refridge unit, over head loading only
VTTX 60' and 85' flatcar equipped with fixed container pedistals for COFC service only
WTTX 89'4" "Twin-45" standard level flat car with tow hitches for TOFC service
XTTX 89'4" flat car equipped with 4 hitches for TOFC service
ZTTX 85' flat car equipped with 30 stake pockets for transporting long poles or pipes
ATTX - 75' all purpose flatcar (center and side tiedowns)
BTTX - 89' flatcar equipped with bi-level auto rack)
CTTX - 89' low level flatcar equiped with partially enclosed autorack
DTTX - 265' Five platform, articulated well-type COFC car capable of carrying double stack containers
ETTX 89'4" low level flacar equipped with totally enclosed tri-level autorack
FTTX 89'4" flatcar equipped with tie down devices for loading automobile or truck frames
GTTX 85' and 89' General American built flat car equipped with collapsable hitches and bridge plates for transportation of trailers
HTTX 60' Flatcar equipped with 38 heavy duty chains, snubbers and turnbuckles for carrying earthmoving equipment
ITTX 89'4" flatcar equipped with special fold away pedistals and 62 tie down winches with chains and bridge plates for carrying trailer tractors saddle back style.
JTTX 50 - 89'4" flatcar with misc devices applied for lessor special service
KTTX 89'4" "Twin-45" standard level flat car with fixed hitches at both ends for handling two 45' trailers back to back (over head loading only)
LTTX 89' Low level flatcar equipped with collapsible hitches and bridge plates.
MTTX 60-85' 60 foot flatcar with stake pockets for gen service or 85' flatcar with 16 stake pockets, 8 per side for tansporting long pipe.
NTTX 249' 5-unit articulated COFC car for transporting containers (spine car)
OTTX 60' Flat car equipped with 36 chains, with snubbers each secured to movable and retractable tie down winches in for longitudinal channels for tansporting agricultural equipment
PTTX 60' flat car equipped with bulkheads space 48'6" apart for transporting plywood and wallboard etc.
RTTX 89'4" "Twin-45/Tripple 28" standard level flatcar with fixed hitches on ends of car and retractable hitch at center of car. For handling two 45' or three 28' trailers (overhead loading)
STTX 89'4" "Twin-45" standard level flat car for handling two 45' trailers, equipped with sliding bridge plates for circus style loading
TTAX 89'4" Standard level flat carequipped with foldaway container pedistals and hitches for TOFC and/or COFC service.
TTBX 89'4" flat car equipped with bi-level auto rack, rack can be either open or shielded on the sides but does not have roof or doors.
TTCX 60' and 89' flat car equipped with container pedistals for COFC service.
TTDX 89'4" flatcar equipped with 16 tie down winches with chains and bridge plates for transporting military vehicles
TTEX 181'9" two unit TOFC car for hauling four 45' trailers or three 57' trailers (over head loading only)
TTFX 187'6" four platform TOFC car capable of carrying four 45-trailers
TTGX 89'4" flatcar equipped with totally enclosed bi-level auto racks
TTHX 60' 60-foot flat car equipped with 18 heavy duty chains anchored to stake picket astings
TTJX 68' 68-foot 100-ton flatcar equipped with 22 screw type tie-down devices and stake pockets.
TTKX 89' flatcar equipped with hinged "B" deck tri-level auto rack. Rack can be either open or shielded on the sides but doesn not have roof or end doors
TTLX 89' "Twin-45" low level flatcar specially equipped by particpant railroads with container pedistals or fixed hitches for assigned corridoor.
TTMX 68' 68-foot 100-ton flatcar equipped with stake pockets and lading strap anchors for general service
TTNX 89'4" flat car equipped with bi-level auto rack without end doors but with sides and roof panels.
TTPX 68' 68-foot flat car equipped with builheads spaced 62 feet apart and 34 transverse tied down anchors with chains used for transporting plywood etc.
TTRX 89'4" flatcar equipped with fixed tri-level rack without a hinged "B" deck. Rack can be either open or shielded on the sides but does not have roof or door.
TTSX 89'4" flat car equipped with coverless enclosed bi-level autorack.
TTUX 50'6" Single platform TOFC car with single axle trucks capable of carrying one trailer 40-48 foot and up to 102-inches wide w/ nose mounted refridge unit,over head loading only.
TTVX 89'4" Low level flatcar equipped with tri-level auto rack with shielded sides without end doors and without or without roofs
TTWX 89'4" Twin-45 standard level flat car equipped with fold away container pedistals and hitches for TOFC and/or COFC service.
TTX 50'-89' flatcar equipped with one or two hitches for TOFC service.
TTXZ 64' to 76' 100-ton bulkhead car equppied with center partition and winch type tie down system for carrying lumber products.
UTTX 256' Five platform articulated TOFC car capable of carrying one trailer per platforum 40-48 feet and up to 102 inches wide w/ front mounted refridge unit, over head loading only
VTTX 60' and 85' flatcar equipped with fixed container pedistals for COFC service only
WTTX 89'4" "Twin-45" standard level flat car with tow hitches for TOFC service
XTTX 89'4" flat car equipped with 4 hitches for TOFC service
ZTTX 85' flat car equipped with 30 stake pockets for transporting long poles or pipes