Gee, I hope this is the right forum
 

It's not exactly a harp guitar -

https://bernunzio.com/product/dyer-s...yle-402-25153/

Seventeen days since anyone posted anything on this forum.

We're busy playing our harp guitars. ;)

That's an interesting instrument, but I don't see any harp strings, or any means to hold/tune either end of any harp strings?

It's a Dyer (Larson brothers built) harp mandolin...
I don't recall ever seeing a Dyer harp mandolin with subs.
Go here to find out more:
http://www.harpguitars.net/knutsen/dyer_mandolins.htm