Who is the maker on this serving knife?

[Qrt.S]

In connection with the bargain with the aspic servers showed in my previous input I got this knife. It has the same tempered Diana Kopf but a maker's mark of JB or maybe OB (?). I have very little reference books regarding Austro-Hungaria and Austria, so some assistance is requested. Who is this maker OB/JB and what town? Please note that the letter on the control mark is impossible to interpret. Anyway, I assume that it might be C or G, but...?
Thank you in advance.

[dognose]

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Trev.