The model I bought was Singer 3105
Stitch length up 5mm, center stitch + Left or Right ( straight stitch )
Also has a zig zag stitching capability.
Circa 1970s , a good solid basic machine.
One currently on ebay item: 191964756706 Cheap for what it is.
I paid £129 for mine but it was from a sewing machine center & had been fully serviced/set up.
Worked brilliant straight from the box.
I don't doubt that there are better machines out there but for a one off bit of trial & error, works fine for me.
Going to have a go at some covers just as soon as the weather warms up.