Selmer SBA serial 52xxx, on the tail end of SBA production.  The are heading towards the response of the early MK VI but they really are NOT MK VI at all.  They are solidly SBA, they just tend to be a little wider than the earlier SBA in my experience, and that as well is likely to vary quite a bit.
This is, I believe, a Canadian market horn, with “CAN” on the bell stamp, and was likely either non-engraved, had a Canadian market engraving pattern, or was silver.  It is hard to say.  The horn has been stripped to bare brass and apparently re-engraved with the US pattern.  it is currently in the hands of a customer but I am helping connect the horn with a buyer/player. It is in nice playing condition, features the custom ordered high F# key, and will be a very good deal for someone considering what SBA tenors are going for these days.