Can't help much on exact age, but from the original proofmarks, sometime between 1925-1954. Reproofed at 850 bar, but chambers NOT lengthened. Marked 65MM. It'd be 70MM for 2 3/4".

Very fragmentary information on Norman in Boothroyd's "Directory". He places Norman in Suffolk around 1900. From the proofmarks, it's clear he was still in business at least as late as the mid-1920's. Your speculation that it started life in Birmingham is a good guess.