Another DP Question on Long Branch Markings

[Sapper00]

So not trying to beat a dead horse, just a bit confused but some markings on a 1943 LB No4 I've come across. This rifle has apparently been a family shooter forever and passed through the generations. It's a proper C marked 5 groove barrel and looks original.

"BUT" it has a very small "DP" stamp on the wrist as well as another on the trigger guard. Not the usual large stamp, these are only 2mm tall on the wrist and less on the trigger guard. No other markings anywhere on the action or barrel.

And the "D" is the gothic style D which is also a bit different.
SO I know, "Never Fire a DP" but also that DP's are usually prominently marked so as not to be mixed with live.

Thoughts? and also be nice and don't call me an idiot for asking. Did someone just stamp their initials on this for prosperity?