This lens is distinct from the 400mm f6.3's I am familiar with - its not a familar tokina or other. I think Spiratone was a US distributor so they would have contracted presumably one of the Japanese manufacturers to make this. googling pulls up a number of spriatone 40mm f6.3's but most are the familiar t-mount, pre-set "generic" type like
these. This one is fixed mount and seems uncommon.
Add it to the lens data base and write a review.
PS I think you meant to write spiratone in your title right?