I am new to the forum, so please be patient with me!

I just purchased a used (7-yr old) 629-6 and when I removed the sideplate to clean & inspect it I found the hammer block was missing. I also noticed that the pin on the rebound slide that the hammer block rides on was broken off.

What is the purpose of the hammer block?
Is it safe to fire the revolver without the hammer block?

The revolver is used only for occasional plinking but I want it to be reliable/safe should I choose to use it for something else.

It's safe to shoot. The hammer block really only exists to prevent the weapon from firing when dropped. Which is less of an issue with the firing pin moved off of the hammer as on your model.

Just dont drop it.

Thanks Nipster

I would not leave it like that.
The hammer block rides between the hammer & firing pin on the more recent guns & between the firing pin & frame on the older models, when the hammer & trigger are both at rest.
It's there for a good reason, and dropping isn't the only one.

A new rebound slide & new hammer block are neither expensive to buy nor expensive to get installed, if you have no mechanical ability yourself.

The gun has lost one of its built-in safety features & should be repaired.
Denis

Another note would be an observation on the "Just don't drop it" approach to the problem.

I'm sure everybody who's been killed accidentally by a dropped handgun PLANNED to drop it & did so deliberately.
Denis