Advice Sought on Mystery HO Collection- Automotive Series Train Cars

I am new to this and have inherited my grandfathers trains. One set stood out to me and I cannot find any information on it such as value or rarity which is surprising considering the internet is huge. Anyone who can help tell me more about this is welcome because I simply have no idea. Trying to get an idea on why they were produced and their value.

In the collection I found there are 14 Roundhouse HO scale models of auto manufacturers. All are new in box and the boxes read,

FMCX 50412 Mercury, 50’ Box Car

GMCX 1303 - Oldsmobile, 50’ Box Car

FMCX 50414 Motorcraft,50’ Box Car

FMCX 50411 Ford, 50’ Box Car

GMCX 1305 Cadillac, 50’ Box Car

CCX 1348 Jeep/Eagle, 50’ Box Car

GMCX 1302 Pontiac, 50’ Box Car

FMCX 50413 Lincoln, 50’ Box Car

GMCX 1301 Chevrolet, 50’ Box Car

CCX 1346 Dodge, 50’ Box Car

CCX 1345 Mopar,50’ Box Car

GMCX 1304 Buick, 50’ Box Car

CCX 1347 Chrysler/Plymouth, 50’ Box Car

GMCX 1306 Saturn, 50’ Box Car

If anyone could help that would be great. I am pretty curious about them because they appear to be a complete set. I have pictures also if that could help.

An FMCK 50412 Mercury 50’ boxcar sol on EBAY May 1, 2015 High bid $46.51 “HO Roundhouse Custom " Show ME " Ford Mercury 50’ box Car NIB FMCX 50412” -----------Current listing for 6-car set $399.99 “Roundhouse — Super Rare to find all 6 cars!!! “Show Me” 6 Car Set–GM General Motors Automobile 50’ Boxcar Kits Saturn, Oldsmobile, Cadillac, Chevrolet, Pontiac & Buick All kits complete–Parts & directions Show Me Lines Custom Rail Car Company is now closed These cars will never be produced again!!!” http://www.ebay.com/itm/Roundhouse-Show-Me-6-Car-Set-GM-General-Motors-Automobile-Boxcar-Kits-HO-/151732347569?pt=LH_DefaultDomain_0&hash=item2353f3e2b1