M1898/05 S98/08 nA - help identifying 2nd ricasso mark?

I have an M1898/05 German bayonet. It's pitted but I can make out the following:

Maker is "Rich. A. Herder, Soligen"; It is post 1915 because it has the muzzle flash protection strip fitted; The spine proof mark date is corroded - I think I can make out the crown and W but no clear date. There's probably a '1' in it.

My question: there is a 2nd mark on the reverse side of the ricasso I can't identify. It's triangular with the flat side of the triangle is towards the handle, the point of the triangle facing towards the bayonet point. It is a triangle dominated by an italic upper case 'D'. There are two lines of writing under the 'D', still inside the triangle.

I can make out the following only

Line 1: D.......pp
Line 2: o...[6 illegible letters/numbers]...o

Can anyone help with an identification? Is it a second makers mark or a regimental mark?

Thanks
Gilo

I'm new to this forum so don't know if I can submit an image but will do if I can

Here's the image of it

Actually looking with a lens I am not sure about the proof marks either. Where I would expect a date to be it looks like a crown over an anchor. Any idea anyone?

Thanks in advance

Durkopp/ Werke A.G in Bielefeld, should be the second triangle marking, the stamps on spine could be inspector stamps, crown about gothic letter.b.r.Andy

Thanks very helpful - this has enabled me to search for more information now too. All the best G