Ah, that makes more sense.
White featherweight = celery, as opposed to the new crappy white featherweights.
The "white" threw us all off.
There is someone here on the board - Lost51 (Billy) - who is an expert on the older featherweights - or so everyone says. ;-) But since I see recommendations daily to contact him, I'm going to pass on the info.
Why don't you PM him and see if he can help you out? There's an older ongoing thread on vintage machines, as well, that you could search out to ask the experts posting there.
Hope your mom gets it fixed.