Quite niche, but might suit a proud Mercian owner!
Really nice headset, I’ve seen a couple of these branded like this but they do seem to be fairly rare.
Mercian marked Tange headset. 1” British.
This has Mercian marked on the locknut and inside face of the top race.
Everything included - this was really, really stuck up with grease when I got it. I’ve degreased it well, though traces remain, and the bearings which I found within the grease are included for reference, some probably rolled out so consider them here for reference.
The faces of the headset look nice and smooth.
There was a bearing carrier in the top, which had decomposed in the grease, while there did not seem to be one in the lower cup.
I would anticipate that as these were a fairly common headset (except the Mercian text) you can identify and replace with new bearing/carriers as you wish.
Externally, the chrome is nice with only minor surface marks in a couple of places.
£27 posted UK by PayPal, fees included.