That's a really interesting little source re: Boosey...
....however, it is also quite puzzling to me. The Authors have not indicated anywhere that many (most, I would argue) Boosey & Hawkes instruments were actually stencils....NOT produced in any facility of theirs.
So...it is perplexing, this resource.
I have here in my shop, for sale currently, a Boosey & Hawkes alto which was made by R&C, and it (as one would expect) sports a definite R&C serial # (01XX), which according to this source places the horn at 1857 . (The horn is from the late 70's, this confirmed by Claudio Zolla over at R&C).
Now if one reads it carefully....it never mentions Saxes per se....just flutes and 'woodwinds'....so I am going to assume this resource actually is not referring to saxophone production at all....but likely just flutes, clarinets, etc. There ARE indications that Boosey actually DID produce saxes in-house sometime in the 30's...but those are very rare to come across -and quite 30's-looking - so that endeavor seems to have been short-lived before they started subcontracting to Amati, Kohlert, and a variety of other makers (R&C included).
One needs to be careful when referencing instruments branded w/ a company which did a LOT of subcontracting out.
As Thom notes, that horn clearly appears to be a Bundy II. Therefore the likelihood is the serial # will be akin to the Selmer USA sequence, or whatever sequence Selmer USA used on Bundy II's.
The horn, therefore, is likely to be from around late 70's-late 80's. What is interesting is the finish, honestly ! Never have seen a nickel (or perhaps silver?) Bundy II.
Basically a Bundy II tenor in decent playings shape is worth at most $500usd on this side of the Pond. And THAT would be a very good price to get for one on a private market sale.
I suppose one can make an argument that the finish may make it worth a bit more....but I doubt very greatly the market would 'buy' that argument.
Solid, sturdy student horns. Honestly I would take one of these over 75% of contemporary student model saxes. It is the kind of horn which, when in good shape, is worth more to the owner (to keep and play) than to a buyer, if you get my drift.