It's a variant on the Autoslim with a large platter. The arm isn't counterbalanced, so it's very heavy toward the front (cartridge) with a strong spring pulling upward to compensate. The tension on that spring is set by a thumbwheel underneath the arm about halfway back toward the pivot from the headshell.
Later Garrards with non-counterbalanced arms, such as the Model 50, 40 Mk II, 40B, 50 Mk II, SL55 and SL55B had a partial counterweight at the rear, with a much lighter upward-pulling spring for tracking weight adjustment.
The arm on yours is the same as was on the Autoslim/P (P for Plug-in). The original Autoslim didn't have a plug-in shell. Your headshell is the same as on the AT6, and interchangeable with the lightweight cut-away version on the AT60, 60 Mk II and SL65 (non-B version) in the USA.
It is capable of tracking down to about three grams. Most likely such a Garrard in a radiogram would have a ceramic cartridge that tracks a lot heavier than that and would be damaging to records. There is nothing to stop you from physically installing a lighter-tracking magnetic cartridge that would work at three grams (some of the current "disco" cartridges, for example) but it's likely that the radiogram doesn't have the necessary phono stage to provide gain and equalization for it. Also, such a Garrard in a radiogram is likely to have a two-pole motor, whose basic rumble frequency is way up into the audible range, around 60Hz in the USA. Radiogram speakers aren't likely to reproduce that low so their users never knew! Component-grade Garrards such as the separately-sold Autoslim, the AT6 and variants named above, and the Model 50/40 Mk II were all equipped with the better four-pole motor.