JUKI K-821 knitting machine is a truly vintage knitting machine. I could not find a manual for this machine. But judging by its similarity with the Silver Reed SK8 and Silver SK101, machines, it was very likely released onto the market in the late-1950s/early-1960s (see my collaborations on why below).

I could not find a manual for this machine. But it looks a little bit like a cross between Silver Reed SK8 and Silver SK101: detachable handle like in SK8 but the additional carriage (also called a “needle selector”) as in Silver SK101. The second sinker plate is probably for the needle-selector carriage.

The needle selector mini-carriage seems a bit more advanced than that for the Silver SK101 machine: it has an almost full-size sinker plate (Silver SK101 has a mini sinker plate attached to only one clamp). The row counter is also of a round slip-on type.

However, the carriage for the JUKI K 821 looks simpler than the carriage for the SK101.
A similar, basic/manual knitting machine produced by JUKI is the JUKI K-851 model.

If you are a proud owner of this machine, I would like if you contact me so we can talk about this beauty more.