They had so many BL-XX models I hope I don't get this mixed up. If memory serves, the 51 does not have an internal suspension. It has a fiberboard (or the like) base under the plinth that has 4 spring loaded feet attached. I think most people remove that baseboard and set the very solid plinth directly on the stand, making it completely non-suspended.
It's a great table. I have a dealer friend who has sold lots of great turntables and he still has a BL-51 with MA-505 Mk II as his at-home reference table. I was looking for one for myself a couple of years ago but gave up the search and went in a different direction when none came up for sale reasonably priced or in good enough condition.
That's a good price for one if it's complete and in good condition.
