Hi Mike,
A quick google shows most restored Cov Eagles of this type use a sliding push-pull (hexag-on) type tap, with a flat slide and cork seals in the body.
However I think I spy in some period photos and adverts an Ewarts-type push-pull tap - the one with the single-ended cylindrical slider with the cork seal attached.
If you want the bike to be very correct, perhaps contact the Cov Eagle marque specialist at the VMCC, or try John Hodson via
https://www.coventryeaglemotorcycle.org.uk/index.html to get the real story.
In either case, instead of the tap screwing into the fitting, there is obviously a couple of brass pieces required to complement the tap: a top bit with a thread, and a bottom bit, to secure the tap in position.
Interesting detail - let us know if you come up with an illustration of the original.
Cheers
Leon
