I've had one of these. It is made of particle board/laminate. You can
replace the piece with a good piece of plywood that has a laminate (Formica,
etc) on it from an old kitchen countertop. You won't have the lines on it,
but you don't really need them.
I suggest that you purchase a new playfield since you will never be
able to level it correctly. Harvard tables usually use a particle
board playfield that can be replaced easily by almost universal
playfield, just make sure the dimensions are correct. You can
purchase them from us at www.foosballstore.com if you need to.
Oh! I forgot to say before that you try buying a large piece of wood,
plywood, particle board, etc and the using a paper playfield. This
will give you a good feel of a traditional playfield and its
guaranteed to fit since you can just trim the paper playfield. Only
problem is that sometimes this can be more expensive then just buying
a regular playfield. Its your choice...