As much as I can gather, DP rifles were primarliy made from condemed rifles or assembled from dodgey parts. However, if an armoury was filling an order and there wasn't enough junk riles to convert, they would pull the balance from stores. So it ispossible that there is absolutely nothing wrong with it.
Also if an arm was made obscolete, it was a candidate to be made into a DP.
The main thing with a DP in service is that it would no longer in the loop for inspection and maintainance as would be with live rifles.
Some other older DPs that I have seen are complete and capable of firing, DP marked everywhere including the bolt handle. I guess that is why DP was stamped, stenciled and bands of coloured paint applied to that there was no mistaking them for live rifles. Some have 'NOT FOR BALL' stamped on them which means that they were good for blank fire.
There is a story bouncing around about a recent incident with an Army Cadet instructor. Story is that a DP ended up on the range and a cadet was trying to fire ball rounds through it but it would not fire due to the striker being cut off short. Click but no bang. The dick head of an instructor checked the cartridge primer and seeing no strike mark, he switched out the bolt with one from another rifle, a live one and gave the DP back to the cadet to shoot. There was a problem and the cadet was hurt.
This could not have been an incident in Canadaas current day DPs as issued to Canadian Army Cadets, have no bolts, no mags, they can't even chamber a round as they are drilled and pinned through the chamber (some would make you cry, minty Longbranch No.4s).
And then there are the arms made into DPs simply because they became obscolete. I am playing with a project Lee Metford that has DP markings. Original finish, well dinged up yet, it's internals show very little use. Without a doubt it was a DP issued without a bolt.
The bore is clean and shiney, bore guages show no discernable wear. More by luck than good judgement, the bolt head I fitted sgave me correct headspace. I have shot it and the spent cases show no signs of distress.
So if the receiver is marked DP, have the rifle checked against specs. It might be just fine.
Oh, and also something to note. I have seen parts with a condemed mark (bolt heads, barrels, mags, woodwork), that have an armourer's cancellation mark overstruck where DP parts were put back into service.