BoobTube videos, that’s what you’re dealing with?  Some models had a separate cover and others didn’t, plus some covers were part of the deck and others had a separate part number.  I’m guessing you have a mower that was cobbled together by someone trying to make a quick buck.  A model 20371 had an MSRP in 2012 of $299.00-$369.00 depending the part of the country where it was sold.  Right now in good condition worth about $50, and yours is definitely not in good condition.  I might be able to sell it for $25 to someone who’s looking for anything cheap.