Scored this old Workmate at local Restore. It is steel and cabinet grade plywood. There is paint on the wood but no saw marks. It is heavy. The moral of the story is if you have a Habitat Restore that stocks building supplies and hardware, you need to check it often. $20.
Mine is a Model 400, and I think yours is too. It's a great tool. I bought mine new, but can't remember how long ago (a senior moment ). Instead of plywood, mine had termite barf (particle board) tops. One night, I left it out in the rain.
I am now more than happy that I did, as I replaced the tops with 8/4 hard maple, and added a lot of dog holes in more logical places. I often use it when I'm working or demonstrating away from the shop. Here it is with my bench-on-bench mounted.
Since that picture was taken, I have replaced the masonite lower shelf with some tongue and groove bamboo.
I also sometimes configure it with a mini-lathe, blast shield and work light.
I bought that one new back in the 70s. Still use it. It has what appears to baltic birch top pieces. I had to replace one crank handle, but otherwise, it's been a reliable tool. I normally use it as my CMS stand.