I've signed a contract with Home Depot for them to install a new
Quartz countertop to replace the nearly 50-year old formica one I now
have. I think the sales lady at HD told me if I removed the old sink
& countertop myself I wouldn't have to pay an extra removal/disposal
charge.

I have an L shaped countertop. Was it customary in the late 50s to
simply nail the plywood top down to the cabinet, or would they have
used an adhesive.....or both?

Anyway, I would welcome suggestions as to how to get the top loose.
My guess would be upward strokes at the overhangs with a hammer,
followed by a pry bar. But if anyone has a better idea, please share.