I googled Goggan upright pianos and got a few hits. One is a picture of the G you posted. It doesn't look like a serial number font, but a brand identifying font.
There is more info to find on Goggan and some discussions, also. I'd google and sleuth as best you can. I didn't see any advertisements with the G front your posted.
On this Goggan (probably an older model) you can see the oval where the serial number would be. I vote that the G is for Goggan and not a tuning reference!
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Richard Adkins
Piano Technician
Coe College
Cedar Rapids, IA
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Original Message:
Sent: 09-13-2019 04:59
From: Ron Bergeron
Subject: Goggan Bro. Upright mystery
Does anyone have an idea what the "G" stands for on this late 1800's Groggan Brothers upright means? My customer was told by an earlier technician stated that it meant the piano was supposed to be tuned to G440. I think he just made it up, but told the customer I would post the question to this site and see what responses we get.
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Ron Bergeron, RPT
Austin, Texas
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