Hi,
My first post on this forum... glad to be here. I've owned a sunburst T-100-D for 15 or 20 years now, I guess, and it dates to 1964 (SN 33941). It has volume pots close to the strings and tone pots away from the strings - opposite of the 3 Gibsons that I own. Considering the hassle it is to work on those pots I've always assumed it was original. When I later got a Gibson I was surprised that their layout was diffferent - I think the Guild layout seems more natural but both work.
Anyway, Aeustus, I think there's a good chance that the layout of your controls is original. It would be good to hear from a few other T-100-D owners of similar vintage.
Eric