All About Pocket Knives

Can you guys help at all with any info on this one? Found early this am on my yard sale rounds. Knives are scarce up here in the tundra, so I've made a habit of asking folks if they have any knives "in the house"? "laying around"?, etc, etc. Well, finally, after thousands of inquiries, these unexpectedly came out early today from the female side of the elderly couple . Go figure. I ask at every sale. This little bugger is solid and tight.
Tang reads: "Iros"-'A diamond shape'?-then "Keen"
Handle material is natural, any ideas what material perhaps? Age? Mfr? My books are a dead end ! Grateful for any info. Thanks guys. -Glenn

Goins says

IROS KEEN NEW YORK c 1924-1925 A trademark used by I. Rosenbaum.

All I've got,

Jeff

Nice little knife - I can't tell whether the handle is bone or celluloid. As Jeff posted, a rare brand, possibly made on contract by Utica Cutlery Co.

Knifeaholic and/or anyone else. The handle material is definitely natural (has bone/horn givens, ie: holes, marrow canals, etc.,and, would celluloids have been used that early?), the color is accurate in the pic. Any idea what the material could be given the age, striations, etc?? This may be a dumb question: Is there any way to tell between horn and bone or any natural ?
Thanks much for any info.
PS, can someone tell me what Goins book is being referenced??
-Glenn

http://www.knifeworld.com/goinenofcutm.html


Jeff