Now and again questions are posted regarding the age of SIF engines. Some of these may be of interest. I'll add more images as I find more points of possible interest.
Late 50s early 60s. No recoil starter, just a rope wrap pulley, Rectangular fuel tank, exposed cylinder head and a curved shield around the cylinder fins.
Early steel, hinged governor vane. Also top mounted fuel banjo on the Zenith carburettor.
Early "split pin " dipstick
Maybe an unauthorised modification with a sump plug replacing the drilled one.
Old style round air cleaner
Later square air cleaner
17" Professional with square air cleaner and anti drip tray . Also plain heavy cast alloy rear rollers instead of the ribbed or plain steel ones on the domestic 17"
Early ignition stator with large fabric and shellac coil and rocking contact breaker points.
Heavy flywheel marked Suffolk Iron Foundry. Later ones with more fins and marked Wipac