Is there a trap in a shower stall built in the 1950's?

There should definitely be PTRAP piped to the shower. It is usually located under the shower in the dirt.

If you look into the shower drain with a flashlight and there is standing water there... then there is a trap present... ;)

MARK

Is there a trap in a shower stall built in the 1950's?

Of course you're trapped. Speaking as one who was out in the field in the 1950's I can assure you that we had plumbing inspectors way back then. Why are you asking? Regards, Tom

Yes, there is...