As such it pre-dates slide guitar in Hawaii.

Are you sure of this? It looks to me like a typical 1930-50s "Hawaiian" guitar, without the raised nut needed for playing slide -- in other words, a convertible Hawaiian guitar. You would use one of those metal raised nuts to play it slide style. But I don't think these would pre-date the Dobro or National patents, and those were built to meet the demand of the Hawaiian music craze you mention. That craze was for slide guitar, slack-key guitar (which never caught on as much as the slide) and the ukulele. I don't know of any commercial instrument with a note-chart on the fingerboard that wasn't a Hawaiian guitar (regular fingering would soon destroy the chart, for one thing), and the open tuning notes give it away, too.

So I stand behind my original response -- it's a commercial Hawaiian guitar, probably made by Harmony, Regal, or possibly even Kay, under another brand, and no earlier (but probably later) than 1925.

Songbob