It works on old Gibson Mandolins
"Secret" Serial Numbers
© Frank Ford, 1998, 2003; Photos by FF, 1998, 2002

Here's the problem. The serial number on many old instruments was written on a paper label and can fade with time and exposure. Not to mention the other circumstances when a serial number can be lost or obliterated (sometimes on purpose.)

This one is really difficult to read, but it's not as bad as some I've seen. After peering at every possible angle, I was able to make out 5_4_0. The second digit looked like a 6 or 8, and the fourth digit was simply lost:

I had the back off this instrument to reglue lots of loose joints inside the body, so I was able to look for the secret hidden number.

First, I soaked the label with water to loosen the old hide glue that originally held it in place:

After a while I was able to lift (carefully!) the label right off the back:

Check it out! Here's the original number written in colored pencil before the label was applied:

Once the back and label dried, the number was even more clear:

I dipped the old label in a shallow dish of clear hide glue diluted 4:1 with warm water:

And carefully smoothed the label back in place, blotting the excess glue with clean paper towels:

After the glue dried, I was able to rewrite the serial number with confidence:

I've used this trick a number of times to reveal the faded serial number on Gibson mandolins and guitars made before 1923. These are the ones with the so-called "GUARANTEED" label. I don't know if the "Master Model" label has a number underneath, or if this feature is found on instruments by many other makers. (At least until recently, Taylor guitars have had the serial number permanently stamped into the neck block under the label that covers the neck attaching bolt holes.)

By the way, I've not used this technique without permission or request of the owner. I figure a "replaced" serial number, if accurate, is better than a missing one.

Just for fun, here's the job again:
The serial number on this F-4 was completely faded out.
In goes a piece of paper towel.
And some nice hot water.
After a few minutes, the label just floats off the surface, and comes out neatly.
This time I glued (hide glue of course) the label to a piece of paper to make it a bit stronger. It was just about to fall apart, and I was just able to glue that tiny broken piece back on.
There's the number!
My "forgery."
Back to original. . .

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