Well, well. Now that is interesting.
I have a copy of said book (purchased for £39.95 from Foyles bookshop in London on 14 September 2000 - still have the receipt) and on page 265 it states:
“The second type, known as the “plate, cover, 9mm Sten machine carbine, MK2”, part no B3/CR 152, was similar to the Mk1 pattern and was also fixed by means of a hole in abutment face and an under-hung lug. The MK2 plate was fitted with a small loop to which one could anchor the hook of the Mk3 Sten sling”.
Is it the same thing?