If you search the Repconn Facility, you'll eventually find a sizable office that's still in pretty good shape. The room has a terminal and a locked wall-safe (which requires 50 lock pick to open), along with a few file cabinets. One of the messages on the terminal mentions a generator room that was converted to storage, which now contains a locked safe that can be opened with the password, "R3pconn." I've looked all over the facility and am unable to find this safe (I searched for it for quite some time on a previous character as well).

Other than the wall-safe that's in the same office as the terminal with the password, there's one other safe in the facility that I remember finding (Easy lock, next to a skeleton with a Hunting Revolver). The password didn't open that safe as far as I could tell, since I needed to use my lock picking skill to get in. I eventually got tired of looking for the safe on my previous character, but I'd like to find it with this one (assuming that it actually exists - I suppose it's possible that it was cut content or something).

It is not in that location.

It doesn't exist. It's one of those many broken stories that don't link in NV.

It does too. It is in the REPCONN HQ, third floor.

Right, the one with a whiskey bottle and a bottlecap.

I got a lot of prewar money and a .44.

What I haven't found is the Mayor of Nipton's stash.

Well, i did exaggrate a bit

And the Mayor's stash is in the gas station down the hill of Mojave Outpost, i believe.

If that was his stash, it was sad. No way he was going to live the good life in the Hub with that. Maybe he never got a chance to put stuff in it.