Genuine AP Lockheed boxed and made in UK.
Front to rear master is the latest model dual master cylinders, which was introduced in 1985 with a stepped bore of 17.8 to 19mm to replace any previous master cylinders from September 1978 to 1988 when the built in servo type master cylinder was introduced.
One of the notable features is the failure switch on the reservoir cap with a yellow identification tab. This replaces all the front to rear square type reservoir cylinders GMC173 / 198 and the GMC192 / 195.
It should also be noted that this new master cylinder has 2 different size metric unions, Top one is 10mm and the bottom one 12mm for the larger stepped bore size to the rear brakes. A new pipe is required - Right hand drive cars is BAU5654
From top outlet on the master cylinder the pipe that goes to the pressure differential valve now connects to the front brakes and can be reshaped in place.
The master cylinder repair kit is GRK1035. The master cylinder gasket is 31G840.