These are truly in "Relic" condition, which is sad to see.
Sadly, as a non-shoulder board collector, I am not good enough to recognize what remains of the Regimental Cypher on one of your shoulder boards. The second one has basically 90% of the Cypher badly moth damaged and missing.
Unlike myself, who does not collect Imperial German Shoulder Boards, Mike K. and Tony S. are sharp enough and familiar with all of the cyphers used by the Imperial German Regiments. If you remain patient, they will likely see this post in good time, and give you some assistance. My other thought would be to send them a private message, asking for help on the ID of this pair of shoulderboards.
I'll try to remember to answer. I apologize for any inaccuracies.
1th shoulderboard 15th Landwehr Corp
2th Feld Artillery Regiment n. 80 (3th Ober Elsassisches Feld Artillerie Rgt.)
3th not completely readible
4th 15th Bayern Infanterie Regiment