I fit that description...I worked about 15 years for railroads, paying into RRB, and the rest of my career paying into social security, a small part was the military, the rest civilian. Once I had ten years on the railroads, my RRB pension was 'vested'. When I retired, I chose to let the Railroad Retirement pay me for the combined amount, as it worked out better for me, than collecting separately from each...(part of the RRB is 'social security', the other tier is a pension). Also, it is MUCH easier to reach someone at RRB with any issues than it is Social Security.