This is a good quality copper/non-abestos type head gasket - of the type that was fitted to Sidevalve Norton engines (i.e. 16H and Model 1 types) through the 1930's up until end of 1947.
It also fits the WD 16H engine, and one is shown fitted to that engine here.
Original head gaskets would have been copper/abestos, but as abestos is now known to be a dangerous substance - this style of gasket is made with a non/abestos head gasket alternative
This gasket is the 16H (500cc) version - pre war part number was 9113. The 596cc Model 1 was listed with part number 9112 - however the stud fittings for both should be the same, with just the internal combustion shape fractionally different - and this should also fit the Model 1, but please email at email@example.com if you want profile dimensions to confirm that.
I cannot confirm what year this model of head gasket was first fitted - definitely early 1930's (and is listed in the 1934 Spare parts catalog), but is possibly the same one as fitted to the first detachable SV cylinder heads - which I believe was approx 1929-30 - if you have an engine that early, please email us and we can confirm dimensions.
In the accompanying photograph you can see the gasket fitted to a WD 16H cylinder head, and a picture of that engine type is also attached.. The same gasket (Part no 9112) continued to be used on the re-designed (retail customer version) 1938-47 type engine offered both pre-war and postward. This engine was of a later design to the WD 16H, although both were manufactured concurrently - but both used the same copper head gasket.
These head gaskets are manufactured for us by a well established specialist UK gasket manufacturer, and as can be seen from the picture - the discolouration of the copper is where they have been annealed ready to fit.
If you have a later 16H/Big 4 model with the 1948-55 Type engine, we can also supply the head gasket for that engine - but it is a different shape, this is our Item number 0928