I had a few, but lost them in a move. They are ANCHIENT AHM tooling that has been around for decades. All the ladders and handrails are cast on and are NOT upgradable unless you do so much body surgery, you would be better off starting from scratch.
I belive these are models of the first phase flexiflo. Other versions had different side stiffeners on lower hopper sides. The paint is well done though.
These were in service on the Boston line, but were gone by 1998. I may still get a few if I run a 1993 or earlier train. These were discharged in Framingham yard.