I say it's worth keeping rather than merching, but these are tricky. They're not all that common. Unfortunately, they're not all that in demand either. Hammers are almost always a hard sell. I don't see many of these around, but I don't see many people looking for them either.
If you're looking to sell now, maybe 5-10k? I wouldn't let mine go that cheap, but I'm not looking to sell mine.
That's my best guess. More opinions would be good. GL!