I think i have to give up on this one... no map I've been able to find report "Tag" (also looked for Jag, Jay, Tay), the only station with a close name is Turn, which is indeed at the head of bay. Looking at the maps there was also a sand promontory at the mouth of the lagoon which does not exist anymore... my guess is either the station has been renamed Turn at some point, or it was on that sand spit and has been washed away since a long time. They usually placed stations on high ground to avoid these kind of things, so i think the station on the spit is a little less probable.
I've found an awesome source for triangulation stations, i'm posting it here.... even if the map is too large to be useful (to locate them properly we still need usgs maps), it's a great checking sheet for station names. It's fairly recent (1985), and in pdf format, which is just awful for maps:
https://thesurveystation.com/NGS/Geodet ... Alaska.pdf
Grass, Green and Turn, circled in red, left to right
I've added Turn to
geonames (position 55.10822, -163.07164) and to our db, as it's possibly our best guess for that station.