From looking at the photos you posted, it looks to me as though you have a homebuilt (or at least not built by Tucker) set of tracks and track carriers. I say this based on the fact that it appears that you have pneumatic tires as idler wheels. As far as I know Tucker has never made track carriers with tires - they've always been solid rubber wheels.
The 300, 400,500, 700, and 900 series all came with steel ladder type tracks. Once Tucker went to rubber tracks the model numbers were/are 1300, 1400, 1500, 1600, 1700, etc. Tucker sold the steel tracks on the later model machines until I believe about 1980 if the customer requested them.
That said, it looks like a nice unit!
Jeff