Shell head marking interpretation

[Pete 100]

Hi there,

I have some trench art made by my G G Grandfather Bertie Arthur Lowrey 28918 WR 274685 who served  with the Royal Engineers in 1917 at Audricq France.

He possibly had a side hustle making and selling trench art?!

From reading previous threads I believe the head stamps are telling me that the shell was:-

75 DE C - 75mm De Campagne - 75mm Field gun.

SD - Compaigne Francaise des Métaux   Saint Denis (brass supplier?)

DB - Establissement Delaunay Belleville à Paris (Shell manufacturer? / pre  war Car manufacturer)

APX - Atelier de Constructions de Puteaux (French state armoury Puteaux?)

15L.13.P (Lot 15, 1913)

Could someone confirm I have understood things correctly and possibly advise what the P stands for or what the crossed out L_II at 2 o’clock might represent…and if anyone has got really good eyes…can you tell me where the tiny cap badge might have come from??

Thanks for any help you can give

peter