I didn't pay ss for over 20 years as a railroad employee. Yes, we had our own retirement system.
We paid into what is called tier 1 and tier 2. 1 is same as ss but is paid out more. 2 is for your spouse,
So they could get a retirement also.
I was told that after 10 years the funds put into ss would roll over to railroad retirement.

if i hadnt taken up hunting i might have became a juvenile delinquent or worst taken up GOLF