I 've had one for 35 yrs, heavist work it's done is making a double walled tent . two weeks ago I bought another , that now sits in a new home treadle stand.
#5 is what I paid at a st vinnys 35 yrs ago... bascily there a model 15 in a modern body ( early 70"s ) The face plate, top cover, presser bar knob and feed dog knob are plastic, of the type that doesn't rott.. nothing inside is plastic ...
But to oil you must remove the top cover and face plate, those are held on with screws ..
This last 237 was an unused machine that sat in a old chicken barn for around 25 yrs +, very dusty outside, inside was like new, about 2 hrs cleaning,
since I have sewn a 7 1/2' x 8" denmi quilt top. never broke thread once...but I refilled alot of bobbins..
. I did have to clean the contacts on the carbon pile type foot peadle also I have yet to see one that had rotted wiring
At 35 I say buy it