Honda-SOHC

It seems to be threaded without the plate. Whatever, tomorrow it goes into workshop to have a new oil pump seal ( missing from the seal kit I got for the rebuild I had) I'll persuade the mechanic to get me sorted. 

Similar but slightly different markings with SBF05-R

This will make you smile my angled ones I have just noticed are marked SBF05 not only is there no "R" but the NGK branding is also painted white wtf?

The straight caps have a pair of slots moulded in - presumably to fit a tool for pulling off the caps - my angled ones do not but being angled easier to remove without pulling on the HT lead.

Might be I have two genuine & two aftermarket - a Guru here will know!

Yes those Brown ones look really shiney compared to mine that are a slightly duller finsh as well as a different shade of brown - might be NGK make different quality caps for different markets.

As Bryan fitted mine I suspect they are the real McCoy.PXL_20240415_145642823 by Macabe Thiele, on Flickr

Funny you say that, as I took a screen shot of the below from David Silver last year, says aftermarket, but marked NGK, and they were red, now I can't find the red ones, only black on their website;

Looking at that i suspect the caliper is as bad so i would use a greas gun to pump the caliper piston out then thouroughly clean, reseal and new stainless piston.
Grease gun method

Standard grease gun remove the fitting that clips on the grease nipple.
Leave bleed nipple in
Remove the steel brake pipe from caliper and caliper brom bike
GENTLY screw the caliper pipe thread onto the grease gun N.B.  it will only go on a few threads as they are different BO NOT FORCE IT.
Pump away and watch the piston for movement.

This has never failed me but does leave the piston full of grease to clean out!