what finish to put on shiny finished old pine table top
 

I just purchased a very old knotty pine harvest table from a flea
market. It has a very shiny finish now & I don't know what kind of
finish this is. I'd like to do a little sanding & apply a new finish.
Since it is a table top I'd like to use polyurethane but I'm concerned
about the shiny top that it now has. I really don't want to completely
strip the current finish. I'd appreciate any suggestions. I've done
very little furniture refinishing