This 50’s Martin 0-15 was flipped and played left-handed for 30+ years. An additional pick guard was added, as well as the original replaced with new guards made from Formica. The bridge was never altered and even the nut showed little suggestion that it had been strung in reverse. Other than securing a few cracks all that needed to be done was to removed the additional guard and restore the original one.
I was worried that the finish would be damaged under the additional pick guard and that the wood and finish may have aged differently underneath. Luckily, other than a little pitting and finish crazing there was almost no difference. A little heat loosened the glue and both pick guards came off with no trouble. I used shellac to fill the pitted areas and to seal the bare wood where the original pick guard went then cut and installed a new celluloid pick guard.
This is a sweet sounding little guitar and now it is back to its right-handed configuration.