A couple of possible suggestions based on entries within the LEMB Sktz Database
http://www.luftwaffe-experten.org/stammkennzeichen.html are DL+?? or SL+??
DL+U?
DL+UI - Kl35 of LKS 3
DL+UK - Kl35 of LKS 3
SL+U?
SL+UW - Kl35
cheers
Peter D Evans
LEMB moderator