Re: Unbranded 19th century Sax
No value as a horn that would be played. Too Primitive.
The C melody horns were mostly mass manufactured in the US. An older model such as yours is somewhat a rarety. It looks to be french. It looks to be nickel plated. I would expect if you really looked under the keys around the upper hand area, you may find some numbers, but that still wont tell you who manufactured it.
I myself simply love these historical relics. I have a few that have been soaking in WD40 for years. I pull them out occasionally and I slowly am able to get them unfused, as most are rusted into place and nothing moves. If yours moves freely, that in itself is a very good sign for a collector.
Unfortunately, the cost to refurbish such an instrument would be more than its value.
Collectors, who do their own work, is your market, if you choose to unload it.
100 bucks would be an expected price from an interested curious technician such as myself.
I hope this helps. I look forward to seeing other input you may receive here.