Etienne
Whatever the Mk V WR-D shows it is not ER655.
From the face of it the two last digits are 22, and the rest looks like EP622 or a number of other alternatives, but the last two digits cannot to my mind even resemble a double five.
Unfortunately Air Britain's EA100 to EZ999 booklet have nothing like this with 40 SAAF Sq
, so I can't make it any better than you in the end....
Cheers
Stig