I think we found a way to roughly or approximately date Harmony Sovereign guitars. The serial numbers do not provide dating information. Sometimes, a date stamp is visible on the back through the sound hole. This does give an indication of year (’F’irst or ’S’second year half). So maybe this is helpful for Sovereigns without a date stamp.
Harmony Sovereign guitars made approximately after 1965 have a short spruce reinforcing plate like this:
Harmony Sovereign guitars made approximately before 1965 have a long birch or spruce reinforcing plate like this:
We have seen enough Sovereigns to believe the foregoing is generally true for H1260 and H1203 guitars.
So to get some idea of how old your Harmony Sovereign is, just feel inside to see how long the reinforcing plate is.
We don’t work on other Harmony models, so have no ideas about bracing in those models.
By the way, you cannot just add a pin bridge to a Sovereign with a spruce reinforcing plate. Spruce is not strong enough to keep the bridge from spliting. This is why we always replace the spruce with Rock Maple. Not to mention the fact that X-bracing and the new plate makes the guitar sound much better.