Here's some pics showing various versions I have from over the years.
Pic 1 First type from late 70s that appeared on higher tier models like the Victa 500 Twin, VC Mustang, VC Sport and Auto Drive. The rest with plastic G4/LM carburettor got the round one with steps like the Corvette. Note the steps in this one and pointy filter cap. This cap will fit on later flatter capped square housings like in the following pictures.
Pic 2 this one is on my 1980s side pull full crank Mustang and also has the stepped slot but flat cap.
Pic 3 on my 1980s SPFC Powerplus self propelled. This has the straight slot.
Pic 4 showing the round type housing on my green early powertorque Mustang with straight slot. My SPFC steel deck mower also features this housing.
Pic 5 square housing on later 1980s powertorque Mustang. Note slightly different print to earlier straight slot housing on the Powerplus from pic 3. This type was also used on the Vortex and presumably the Mustang GTS (basically a white Vortex) that came after it in 1987. Note: many upper tier steel deck models and all thumb latch alloy deck models from the late 1980s received this one as well. It seems at some stage during this era, they dropped the round one altogether as I have an entry model green steel deck powertorque with this square controller.
Pic 6 a printed version from a later model from the 1990s sometime. The transfers varied over time as well.
I'm glad we brought all this up as I never noticed a lot of these details myself until now
