Question about Hardwood floor refinishing

bfan781

I have a question about refinishing hardwood floors. I have recieved a few estimates to sand, make some patches, and poly with gloss. Half the estimates say they are going to sand, apply a sealer, then two coats of poly. Another guy just sands and applies poly, no sealer. Is the sealer a must? The guy who doesnt do it is a guy how comes recommended but I wanted to find out what the deal with sealers are? Do you really need to samd it? The are existing floors from the 50's.

Floor Doc

If you are going to sand it , you need a base coat , and two top coats.