Heres some pics of Mk IV RAF Flying Goggles and Accesories for reference.
The Mk IV googles had numerous upgrades during its short lifespan with a few variants.
Markings in order of issue.
Mk IV 22C / 111
Mk IVa 22C / 136
Mk IVb 22C / 167
The main issue that I can point out to any collector looking to buy a original set is that delamination to lenses is normal and to be expected . If it does not have any at all , the lenses have been replaced .
Hope this helps .