It might be covering up a basic pine subfloor. Linoleum was often used in the 1920s, placed on top of the pine. All that you can do is “dig” and see. It would be appropriate to replace the current material with true linoleum. Or have new hardwoods installed to “match” the old.

A 1/4" sounds like several layers of vinyl or linoleum products. Be VERY careful when removing anything that is permanent from a home built in the prime time of asbestos and lead.

Photos of what you are seeing would be helpful.

I'll take impossible to know for sure without selective and careful demo for $100 Alex!

I had a 20s midwest house and the kitchen and back hallway didn't have the nice oak of the formal rooms. It had a pine subfloor and linoleum with parquet glued on top. Unsalvageable. (You can do wonderful things with new linoleum--not vinyl--with borders and great colors. It's very nice.)

I would expect that your bathroom had (maybe still has!) tile floors.