Yes on the 15-91! I've had one here in a cabinet for several years, but not used it. The plug wiring was frightful, and DH rewired it some time ago, fitting in a new light. But with my Elna SU Air Electronic in the shop, it was next in line.
After straightening out issues with the presser bar and feet, it is absolutely delightful to sew with. Mine has a knee controller, a lovely thing for slow work, and the big bobbin is appreciated. No-nonsense is a good way to describe this machine, Montalto! My Elna might just sit for a while. Rather amusing to replace a 1980 machine with one from 1952.
Dianne in Colorado