After months of working at the lock, finally worked out the combination. But wanted to share what the lock looked like, so if someone finds one, they can see what it is.
Here is the lock as I got it...
Yes, it is a model 1951
This one was made in 1962. (Amazing that this thing is already over 50 years old!)
Cleaned and opened!
This is a predecessor of the 8088 padlock. The two locks side by side...
Instead of being upraised like the 8088, the 3511 has the S&G logo cast into the lock body. Note that the location changes. 3511 was made in Rochester, New York, while the 8088 was made in Nicholasville, Kentucky. (Both are in the United States). Why they got rid of the old style logo that had so much class is something I'll never understand.
When the lock is open, this button can slide up, opening the change key hole, allowing the combination to be changed. Am sure there are threads here on how to do that. If not, let me know and I'll write one up. More specifically, on the 8088, it slides up. It is not sliding up on the 3511. Not sure if that is due to some difference in function design or that the lock is not functioning correctly. If you know, please post the answer!
On the 3511, the model number is hand stamped on the back of the lock, and below that a cast section showing that the patent is pending...
On the 8088, the model number is cast, along with the patent numbers.
There is a number for identification on the shackle on both models. The 3511:
And the 8088, which also has a clip on the shackle just above where it fits into the lock body when locked:
The next change that noticed is the number and location of pins that hold the back cover on. The 3511 has two pins on the top of the lock, and one on each side of the lock. The 8088 has one pin on top and two pins in each side.
That about covers the difference between the two from what I see. Enjoy!
Pretty sure the original factory combination would have been 10-20-30, same as the early 8088 padlocks. But the later 8088 and 8077 padlocks have a factory combination of 25-0. Since I have not been able to open the change key hole, the combination is whatever it was before I received it, 34-10-23.