Since the mid 1990s MTH has created tooling for about 75 freight cars in the O scale Premier line. There were several new releases every year until about 2002. Then their was a pause before a second wave of newly tooled freight cars with excellent detail began to appear in 2004. Since the mid 2000s the older MTH Premier freight cars have received revised trucks and couplers and enhanced details. Most, but not all, of the older cars have received upgraded underframes to accept 2 rail trucks and Kadee couplers.
Excluding the dozen plus MTH premier boxcars some of the very well done MTH O scale freight cars introduced over the last decade include:
The 36' wood reefer, 40' steel reefer and R50B express reefer all introduced in 2004.
The war emergency composite hopper from 2004.
The 41' flat car from 2005.
The fishbelly hopper introduced in 2007.
The 70 ton 3 bay hopper from 2007.
The steel and composite GS gondolas introduced in 2009.
The four wheel bobber and the UP CA-1 cabooses are excellent models.
All of the cars listed above are from the steam or steam to diesel transition era. For more modern diesel era cars MTH has also introduced the following.
The funnel flow tank car from 2004
The coke hopper from 2005
The 60' flat car from 2007
The earlier diesel era MTH Premier cars to receive significant detail upgrades include:
All of the covered hoppers. This includes the 70 ton PS-2 and the 100 ton 2 and 3 bay ACFs, PS-2CD, Airslide and Canadian Cylindrical hoppers. The 4 bay Canadian hoppers are particularly nice.
The center beam flat car.
The 20,000 gallon 4 compartment tank car.
The CN/Auto Train auto racks.
The 100 ton 4 bay coal hopper.
The Coalproter gondola
Steam and transition era freight cars that have received detail and underframe revisions include:
The 50' flat car.
The 50' gondola.
The 2 bay offset side hopper.
For more you might want to check out the O Scale Freight Car Guide. 
https://ogrforum.ogaugerr.com/t...le-freight-car-guide
