Time and place for this shield boss?

[Sean Manning]

I had noticed the Branov boss was in two halves, but I'd wondered if it might have been welded down the middle and later split.

I can't find any scholarly articles on the Glauberg boss specifically.  Most of the results for "Glauberg" on JSTOR are in German, but even then adding "Buckel" or "Schildbuckel" produces very few results.  I'm not really seeing anything on Academia that looks relevant either, although it could be that I just don't know how to search effectively.

The repro is 27.8cm high, 19.5cm wide including the flanges, 14cm wide on the interior, and about 6cm high at the ridge.  It's one piece and 14ga steel.  Definitely meant to be used on its own, although a bit larger than it needs to be for that purpose.

I think the place to look would be the preliminary and final reports on the excavations (which will be in German).  Many European countries require archaeologists to publish those promptly to remain eligible for grants. I don't know where those are published, but one of the previews of the book Celtic Art in Europe: Making Connections points to the volume

H. Baitinger, und B. Pinsker, Das Rätsel der Kelten vom Glauberg: Glaube - Mythos - Wirklichkeit: Begleitband zur Ausstellung des Landes Hessen in der Schirn-Kunsthalle Frankfurt 24. Mai bis 1. September 2002. Schirn-Kunsthalle and Hessische Kultur GmbH: Stuttgart, 2002.

Its a companion volume for a museum exhibition so its probably well illustrated.  I doubt there is anything detailed in English on late Halstatt and early La Tène arms and arms unfortunately (although the book by Canestrelli covers La Tène arms and armour south and west of a line from Veneto to Northern England.