I worked at the R.M. Hollingshead Co. from 1949-1959  (it is the large building visible in the picture behind Olga's)  and every day  I ate lunch at Olga's. The Olga's  shown was opened about (I think) 1951.

If you look directly across Federal Street from  the big Olga's to the left of  Warren-Webster, there is a long row of houses. Attached to the end house is (or was) a one story yellow brick building about the size of a 1 1/2  car garage. That was Olga's original diner. it had a little counter with a couple of stools and a couple of tables  with four chairs each. It was always crowded and had a waiting line.

It was the only place  to eat in walking distance and there were a significant number of  business's in the immediate area. As I heard at the time  Dick Hollingshead  helped Olga to get the necessary  loans and whatever to expand so we employees (and others in the area) would have a place to eat.