This is an old post but I hope it still gets through to you.

Your sax is an antique Martin but with the name Kingston stenciled on it. It is modeled after the Martin “Handcraft” and the “Handcraft Troubadour” (not sure which).

The Handcraft was a pro horn. It has the split bell keys, meaning that the Low B is on the other side of the bell than the low Bb (Apparently not on the soprano).

The Troubadour has an interesting key mechanism: only two RH palm keys that do the work of three. The altissimo E/F vent key is eliminated but the function is not. When you play high enough (high B and above) a double spring "activates" the chromatic side C key as the altissimo E/F vent key. This sounds like a kinda freaky idea, but this same feature was found on the late King Voll True and early Voll True II -- which was produced at about the same time (and for about as long :

The serial number on my Kingston tenor is 21309 with a matching serial number on the neck.  Depending on the condition, the horn is worth between $400-$1100.  I've done a lot of research on this horn.  Email me and I will send you all the information that I have.  [email protected]

Here is a much older post on a Kingston.