Problem Solved

I couldn't find an appropriate drain for the vanity... at local stores... because this was made by Crane in the 1950s.... it has an oversized opening.

 I had to consult my good friend... Google.... and find the right part.
Googling vanity drains didn't work because all I got was plumbing parts for plain, ordinary modern day plumbing fixtures.

So, I thought about it and decided I should look for plumbing supply companies located on the east coast where it would be normal for people to be gentrifying neighborhoods which were 200 years old... and renovating a 'this old house'.

Found what I needed at The Renovator's Supply Inc....BINGO.... another step closer to water.