The black disc at the base of the steerer tube, what is it? Is it a crown race – i have zero experience of 1.5″ tubes? Does it come off..preliminary attempts unsuccessful, though i havent gone medieval on it yet in case it isnt supposed to come off?

Advice please.

Yes it’s a crown race, and yes it’ll come off.

Strange looking crown race but yes it must be. You’ll probably find the seller needs it back to complete his headset.
Use a stanley knife blade to gently edge it up the steerer enough so you can get a screw driver in.

Its come from my bike..im prepping it to send for a Mojo service and fix a travel issue. Cheers folks.

Just leave it on then.

Won’t hinder Mojo in any way, and will make it quicker to re-fit the fork.

is it a 1 1/8th steerer that goes into a 1.5 head tube? Could just be oversized to create a cover for the bearings.

If you’re going to be putting it back on the bike why do you need to take it off?

There’s no need to remove it in order to send it to Mojo…

P.S. blades are for cutting things, screwdrivers are for screws. sheesh!

Dont want it to get lost at Mojo – will they be OK with it remaining on?

yes.

Aye, just spoke to them. Theyre fine with it staying on. Good stuff.

Adstick, blades and screw drivers can be used for other uses, other than there original purpose by non-pedant’s, who don’t need every specialist tool available to do simple job’s. 😉