Spin-on cannister type oil filter from Borg & Beck.
Part number is BFO4003 and is equivalent to GFE227.
Suits the following among others:
Triumph TR5, TR6, TR7, Stag
And other Triumphs with spin-on adaptor.
The filter measures approx 75mm in diameter and is 80.5mm in overall length. The thread size is UNF 3/4''-16.