This situation is what I love to do and after a few hundred refurbishings it becomes pretty routine. Conn Straight neck C meodys are my preference to work on.
1923 was a major C melody year for Conn. Most Conn horns produced in 1923 were C melodys.
Today the market is full of these wonderful 1923 horns needing refurbishing.
Since production ended around 1930, there simply were not made for very long.
But, once they are finished, they play better than new. I am assuming yours is a Conn.
I completely strip a horn down. Rollers must be removed and 50% of the time they have to be broken and then replaced. If all 5 of your rollers move freely, you are blessed going in.
1923 is when Conn added the pivot lock screws. These also can be a major burden, so feel blessed your horn does not have them or blessed if they come out easily. There are 6 of these. The 1923 horns also do not have the cumbersume fingernail G# key. I find the Fingernail G# to be just too heavy, like moving a refrigerator if it is not set correctly in tension.
The tuneable neck has to be dismantled. This also can be a major burden. I recently picked up a custom made tool for removing the lock ring. This custom tool makes the job much easier.
After the horn is cleaned and polished and dents removed, cages are straightened and any resolders performed, the refurbishing begins. Each key must be properly fitted to its place on the horn and its relation to any and all keys in its assigned area. The proper Conn Reso pads are then installed. The correct pad will feel it is too big for its key cup. Properly installed it fits very tightly, completely into the cup, and no glue used. When the key is depressed, it closes perfectly to the rim of the rolled tone hole. After each pad is installed and checked to fit accurately to its tone hole, the cork teflon and felt is added.
That is a very short version of what it takes to refurbish a Conn C melody.
Expect 600 bucks or more for the work. There are a lot of overpriced egos out there, so check around. Use someone with experience in them.
The Catch 22 of the C melody is, most players feel they are worthless, so they sit unrepaired. The cost of the repair is higher than most players want to pay for one of them.
But, if you have the ability to playtest a properly set up Conn Straight neck, you will become a Fan also...
Good Luck from Cincinnati