Oh my nemesis.. Mosler 5-H Lock
you are correct, it is a 4 wheel lock. Mine was also hard to turn after I picked up all 4 wheels.
After failing to graph it and manipulate it open, I ended up using an auto dialer to open the one I had..
If you knew the the combination, and let's say it was set to 20-40-60-80, then this is how you would dial it open:
Dial Left past 20 four times, stop on 20 the fifth time around
Dial Right past 40 three times, stop on 40 the fourth time around
Dial Left past 60 two times, stop on 60 the third time around
Dial Right past 80 one time, stop on 80 the second time around
Dial Left until the dial stops at 16, the dial will not be able to turn any further. Turn the handle to the Left to retract the door bolts.
Here are a few photos of the one I opened:

auto dialer attached to the door with magnets

look how thick those doors are!

inside of door, showing the stops around the door edge, and the cover plate , round chrome thing is the wheel pack attached to the door.

inside door cover removed to show the lock body and brass lock bolt facing up, combination wheels removed already

The combination wheels removed from the door, notice all the gates lined up as they needed to be in order to open the lock:

here are the combination wheels removed from the crub and placed next to each other.

This safe lock is pretty forgiving and in my experience human beings are super lazy and predictable at setting combinations, so dialing combinations that only end in 0's or 5's is your fastest way at opening it. No need to try every number such as 31, 32, 33, 34, 35, 36, jut try 30, 35, 40, 45, 50, 55 and so on for each wheel. Doing this reduces the number space dramatically down to only 160,000 possible combinations. down from 100,000,000 (100 million) Now could the combination be set by someone to something like 17-32-66-91 ? yes, sure, but people tend to go with easier to remember. I also think that if that was the combination, but you dialed 15-30-65-90, the lock would be forgiving enough to still open for you.
Having said that, if you've never worked on safes before, and this is your first time understanding how a safe lock works and dials open, this is not going to be easy. Can it be done, sure. but we're talking weeks or months of learning and work.. not dialing for 5 minutes and listening for clicks like they do it in old movies.
You *could* get lucky and have the safe be set to some super easy combination such as 50-50-50-50 or 25-50-25-50 or 10-20-30-40, which is certainly worth taking an hour to dial all the easy stuff to get it out of the way.
There will only be 1 contact point on this lock because it is a friction fence lock. Graphing is possible.
So what do you say? you up for the challenge?
Squelchtone