Not that I recall seeing before. A common mark was a red printed "2" on the label or back brace. IIRC, sometimes a "Z" instead of a two...Is this a code for Second?
The 'SPE' designation was used for instruments that were set up or ordered with features that were not standard for the model. It means the same as 'Special' or 'Spec.' and it was sometimes written as a suffix after the model designation and sometimes ink-stamped on the label or somewhere on the back inside the guitar. ( See 'The Guild Guitar Book' - page 48 and 164 - 'Special Orders')Is this a code for Second?