You have a Silver plated Conn Straight neck New Wonder Series I C-Melody, which is one of the most desired of the C-Melody horns. A few years ago you couldn't have paid someone to take a C-Melody off of your hands, however recently they have enjoyed a bit of a renaissance and are being collected and played once again since the 1920's. Some horn retailers are selling these in working order for around a grand, although I wouldn't hold my breath for that kind of value....yet. You likely paid the tech to overhaul it about what the horn is likely to fetch ($400.00 to $600.00), but if it plays and looks nice, why not hang on to it and enjoy it? Short of buying a vintage C-Melody mouthpiece (not always the best choice), there are a few quality mouthpiece makers making them today, including Ralph Morgan. Some smaller bore B flat Tenor mouthpieces can be made to play well and in tune with these horns too. Here is an excellent site that you will find informative and entertaining: mysite.verizon.net/res8o1o8/cmelody2.htm

C melody saxophones are roaring 20's trinkets. The value is little or nothing. That's why they are so available. I guess that it is a collector's horn, rather than a players horn.

You can find a lot of Conn C Melody info at cybersax.com (including info on some new C mouthpieces). They seem to think that well-restored ones are worth $900 and up, but I have no idea whether they ever actually collect that much...