While I don't not track current sales prices certain small production SW models with unique features in high condition tend to be decent investments, personally I do not purchase them to make money, I buy them because they are really great pieces of history that cannot be reproduced.
The "Pre" Model marked Combat Magnum is a prized piece that no serious SW 357 collector should be without IMO,
The amount of 6 groove tang versions even smaller, and while AFAIK there are no 6 groove nickel CM's it appears there are fewer nickel 10 groove tang pre model marked 19's than 6 groove tang blue ones making them the rarest of the rare, if a nickel 6 groove exists well, it's even rarer.
I have never come accross one in the wild or would have bought it despite the asking price ( ok within reason) mainly because the chances of ever finding another is low.
Looking back the guns that I fealt I overpaid for 10-20 years ago are now worth way more than I paid back then which supports the saying "You don't always pay too much for a SW but sometimes you pay it too soon".
My lowest serial Nickel CM is a 19 (no dash) Serial K391560 Shipped Feb 1961, Interestingly has a red ramp, white outline rear and wide TT/TH which I consider "The works", since the OP's gun has the basic features it makes me wonder how many or if any of the early nickel pre 19's were basic or had "The works"