You got an old one! The oldest I have come across is from 1923. The tension assembly was tiny on those early machines. You can get a slide plate from sew-classic.com. It is a reproduction. May look for an original on the auction site, but they will be more expensive. I will say that the repro didn't fit as well, it sits a little higher than the throat plate. Is there a red oil wick in a little coil spring-like thing in fron of the bobbin case? If so, that should stay there. I tried picking it out of my first 99. I love using Tri-Flow on these old girls. They may be sluggish now, but with proper lubrication, they will be stitching smoothly! I had a completely frozen 99 moving in 24 hours with Tri-Flow and Liquid Wrench.