The 375, while 16,000 of them were made, very few are for sale at any given time. Even fewer are in really nice condition, and of those, you usually will pay better than $400.
You stole that one.
The cartridge, while it never was popular, is quite a capable cartridge.
It is good for just about anything on this continent out to 200 yards and beyond. If you handload, you can do better than that too.
Congrats and let us know how you like it.
Also, check out the Marlin forums that GB set up for us.
That is where eventually, you will find a boatload of information regarding anything Marlin.
Ranger