Like Robert, I have a couple of older RS single volume catalogues, from 1984 & 5 in my case.
They also show the item codes as above, and also list all item codes in a purely numerical index at the rear, which sent you to the page number.
I seem to recall that in later catalogues, or maybe the CD versions, there was a second numerical item code index, which listed the manufacturer.
If anyone has a copy of a later catalogue, or is able to read the CD, they might be able to come up with a maker.
As far as I can tell, it's a plain iron coated bit, but with a little hemispherical bobble on the inner end, unlike Weller Magnastat, or some of the Antex temperature controlled ones.
The other good place to ask might be Vintage Radio Forum, who have a number of old school and helpful members. https://www.vintage-radio.net/forum/
Not the best of scans, but this is the relevant page from the 1985 catalogue;

Bill
Edited By peak4 on 08/12/2022 01:58:09