It may be for a Singer 301, but it doesn’t look like mine. The one that I have is the Singer Model 316 “Monterey” Folding Table, and has an opening of 7 1/8 x 16 5/8. The Singer 301 or 301A Shortbed fit it, along with the 400-series machines (404, 401A, 403A, etc).
CD in Oklahoma