Bo i'm no expert but information about Boelckes E.III it's very scarce.
As you know Boelcke was greatly involved in Halbertstadd biplane (the very first biplane scout used by german air service), but before that flew one of fokkers E.IV prototypes (122/15) and beyond fighters.
Boelckes E.III, that this humble modeler knows, was 422/15. You have a nice picture of it in Datafile 15 page 4.
If you want more references try Blue Max Airmen Series Vol.1... i don't own this book but i guess that there are a couple of Boelcke Eindecker pics there.
Sorry if i can't be more usefull.
Cheers