The SA-950 line has been around under different names for a long time, at least since the mid-1980s (for example, Sumiko Premier MMT
is the same tonearm). After the world grew tired of Rega RB300, these Jelcos became the "default" OEM tonearm on a lot of turntables, from mundane to exotic.
Technically, Jelco took JVC's "put all bearings in one plane" idea as implemented in UA-7045
and added a small viscous bath for damping in both axis at once. Antiskating is with a dial and a spring. Counterweight is loosely screwed onto the stub and has a dial for rough downforce setting. Newer TS-550S
has a slightly different, and probably better, counterweight arrangement.