Case back removal and pressure testing

[morimotom]

Hello everyone,

First of all, thx for the nice welcome! I'm learning quite a bit (I think).

I have a question, or perhaps it is an observation, regarding watches being sold here. I notice quite a few have their case back removed, presumably so a potential buyer can see the movement and verify authenticity.

If one were to purchased piece like this, should it be pressure tested upon receipt? Or is its basic water "proofness" still maintained once properly reinstalled?

I did a search for "waterproof" and looked through the first couple pages but didn't find a similar question answered.

Thx, and I look forward to your responses.