Variations in burndy socket design on early NAC-52s?

Do the early NAC-52s with the chunky non philips non naim system remotes have slightly different socket design on the 52 and the 52 ps? I've just had an issue with a Burndy and it doesn't seem to fit. It's a non naim one that shall remain nameless (groan) but I wondered whether there was a logical reason? It's supposed to fit both 52ps and supercap. My naim burndy cable has different guiding lug shapes to the other Burndy so I'm thinking they might actually be different in the very early 52s.

Is that possible?  Subtle variations in design are a good reason to stick with the original naim cables as at least they'd account for it.