Jo-He-Ky - Josephinenhütte-Heckert-Kynast, Kristallglas-werke, Akt.-Ges., in Petersdorf im Riesengebirge , Prov. Schlesien (Preußen).
Was the amalgamation of 3 German glass businesses in October 1923.
Josephinenhütte established 1848;
Fritz Heckert Petersdorfer Glashütte, in Petersdorf im Riesengebirge, Prov. Schlesien (Preußen). established 1866;
Refinery - Neumann & Staebe, Hermsdorf-Kynast, Prov. Schlesien, Preußen. established 1906.
Data from 1925 source in the Glass-Study
Warmbrunn was listed under Prov. Schlesien in 1906 (Source not yet in Glass-Study)
and
Schaffgott'sche (Gräflich) Glasfabrik Josephinenhütte, were then in Schreiberhau, Schlesien. Heckert was at that time in Petersdorf.
All I can find in Warmbrunn were a couple of glass dealers but no reason that one of the businesses was located there at another point in time.
As Fritz Heckert does not appear to be personally involved in 1925, it can only be that he is German, regardless of later, 1940s, border changes.