Dave,
Grid numbers are repeated evry 100,000 meters. That is why we have the letter identifiers called a prefix preceeding them. and thus the present confusion between YA and XA. It caused a lot of confusion because maps got read wrong, especially in aviation when you can cover several grids in a days operations. Once, on my second tour a Capt. at Bn. gave me a set of grid coordinatesto go execute a recovery, and when I looked at the map it was dead in the middle of the Ashau Valley. When I asked for gun support he said naa the area is secure and has troops. When I got there it had troops alright. NVA by the bunch and no americans for 20 miles. I was lucky to get out alive and when I called and asked they gave me the new prefix which was along the DMZ in the corner by Laos at a ARVN firebase. When I got back to base I went looking for that Cpn and got intercepted by my company commander who assured me it would be taken care of. That staff puke never issued another set of recovery orders as far as I know. I don't remember what happened to him nor care. That is what happens when the Prefix is misread or left off.
BT