On 8 Jul, 09:07, "Dave Plowman (News)" wrote:

More likely a mix of Unified and Metric, if BL.

Longer-lived vehicles used 3 thread standards (and of course BA too).
UNF & Metric were obvious and needed spanners, but coarse threads into
cast iron could remain as Whit for a very long time, although not
often needing to be worked on at the garage-mechanic level.