Maybe would be the only answer anyone can give you from here.

A lot of it would depend on whether or not the installer did so at the time.

not to mention at this point if they did, it would probably be something like a rosin paper, and with 50 yrs passing it would be so brittle that it would no longer serve any protection. So might as well as assume there is not.

By underlayment do you felt or rosin paper or an actual underlayment plywood, particle board or t&g lumber?

By underlayment i mean anything between the oak and the subfloor weather it be rosin or felt or what ever else........

My 1905 home had some kind of tar paper underlayment downstairs, though I think the floors were redone in the 1930s. Such a thing has been in use for that long, but whether or not your builder used it is another story.

In my understanding, when 1x lumber laid on the diagonal was used for subflooring, some type of paper was laid over subfloors for insulation. Some people still used it after subfloors were mainly plywood. Some architects still spec it today even though it's probably not needed. Your house likely has plywood subfloor so you'll have to look to find out. You can either use a Fein saw or a hole saw to remove a small piece of flooring and see.

My subfloor is 1 inch thick pine planks that are layed diagonal. There is a utility closet where the floors stop at and there is a piece of plywood in that closet. I can see the edge of the oak board and there is a quarter inch gap between the oak and where the plywood starts. I can see the diagonally laid pine planks but there is no underlayment there. It might have been removed when the plywood was put in the closet. The closet holds the water heater and furnace. When they took up the original floor that was in the closet, they may have removed any underlayment before putting down the pine. Where the edge of the hardwood stops and where the plywood begins, the area is too small to be able to see if anything is under the oak. I would have to damage a piece of the board to find out.
It is not important that i know im just curious.

Removing a baseboard might give you some clues.

You are going to have to remove something and take a look ... because none of us was there when the installer was working.

Trick I use sometimes with old houses.

Get under the house if possible. Look for gap/s in the sub-floor between two floor joist (may need to move some insulation).

If you find a gap 1/2" or so between the boards. Take a utility knife with a long blade. Cut/score along the edge of the sub-floor boards using them as guides. Once the cuts are make along each board and another across one end. A small flat screw driver, wire etc can be used to pull the underlayment out from gap if it is there.

Most of the undelayment I have found in older houses has been roofing felt.

May help. Cut along the red lines.