Clearly made in the same factory as thomann’s own 4.4mm zither key (<a class="article link" href="thomann_zither_and_hammered_zither_key.htm">Thomann Zither and Hammered Zither Key</a>) as the design and handle are identical to the millimeter. The square socket in this one actually fits the Gewa 5.5mm zither pins also available from thomann, whereas the last batch of zither keys I ordered from thomann didn’t.
Pity it’s twice the price, but at least it works.