The 700 series is famous for broken
gears and worn out timing belts.
[Half century career as SM technician, all or recently in Madison,Wi; founder / moderator of several on-line groups for vintage SMs]
That is not true for all 1970s Singers. No matter, they announce their model, not their age. I'll take one of the last all mechanical machines from Kilbowie /Clydebank from that era. There were some Singer Fashionmates, made in Italy, that had no plastic gears, the 237, I think, that are among the good ones. But,by reports, not all 237s were built with the same gears.
*(Now, find a vintage sm which Holman has wrongly disparaged, and you will have a bargain, so great is the weight of his opinion. Like Ted Williams on bats or fishing tackle.