"Standard directory of proof marks" by G Wirnsberger page 156.
You're right about Zabala.
Lifted from a google search:
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Gunmark Kestrel
Q I have a Gunmark Kestrel side by side shotgun. I am trying to find out
how old it is etc.
A KESTREL is a line of side by sides manufactured by ZABALA Hermanos (located in EIBAR, SPAIN) ;the manufacturer mark stamped under the chambers and on the water table is certainly a Z left of a H in a shield For some informations, have a look at www.aceros-de-hispania.com at the ESCOPETAS PARALELAS section
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