If the letterhead is from the 1920s or 30s it is very likely that it is engraved rather than typeset. Note the variations in letter size and details, especially the L.
Not a lot in the way of digital fonts that recreate the effect, particularly the K and S.
Some general similarity in Piranesi, designed by Morris Fuller Benton for ATF (1930) and digitized by Bitstream:
http://www.identifont.com/show?25S
also Dorchester Script by Monotype (1939)
http://www.identifont.com/show?J3
Perhaps closer is a new design, Almibar, by Manuel Corradine (2012)
http://www.identifont.com/show?2WQB
Don

Thanks Don

I honestly don;t know when it was designed exactly but know that my great grandfather started the business in the early 20th century. I'll try the suggestions though

You're welcome Mark.
As for possible metal types, I checked the scripts in Jaspert's _Type Encyclopaedia (1970)_ and none were closer than the digtal ones I mentioned.
Don