I am both geocacher and letterboxer. I have made 3 of my 18 letterboxes a letterbox hybrid on gc.com. I have posted the clues on letterboxing.org AND gc.com. The letterboxers get the letterbox type clues (as they don't own a gps) and the geocachers get the usual information. Once you find my letterbox hybrid, you will find a handmade carved stamp, log book that works for everyone, and also trading items too for the cachers. I just label the stamp with DO NOT TAKE signs and what not so they don't get confused if seeing it before looking at the cache listing. Only one time have I had someone take my letterbox (it was a cool stamp) since then I just don't put out my *best* stamps. There have even been some cachers who have gotten their own stamp after finding a few of mine