I tried to find your folks boat in the Alden history but struck out. And mine was designed over 20 years later, 1959. Alden and then Alden Design Co designed a lot of boats in 100 years that the design firm existed.

What little I can find out is Alden referred to these as "D" ports. Partly, they're a result of the raised doghouse that was in style in this era.

But the D shape is etched in this period of design outside of boats. The windows in the same year XKE Jaquar were almost identical(but who did the D?). Alden put the port shape in a few sailboat and motorboat designs in the same time period. Then the doghouse sort of lost favor I guess so smaller(safer) ports took over(?)

And it's no simple D shape. It's an elliptical outline that doesn't look right unless, it's "right".

Now they're just pieces of the history puzzle of the designers that were working then. Too many details of the history are lost now.

If you ever find the Alden Design # of your folks boat, let me know. I still have contact with one of the Alden designers that's now on his own.