Pictured above is a photo of New Orleans musician, Bob Ice and his 2-string plywood bass fiddle. The photo was taken by P. H. Gaurisco for the Times-Picayune and is dated July 19, 1959. A little bit of Google research turned up some info on this DIY bass and its player.
According to an interview with Bob Ice's fellow musician, quintessential New Orleans cornet player, Manuel "Moose" Zanco taken just four months after this photo (archived by Tulane University here), the bass is made from a few scraps of plywood, two genuine bass strings and 'hardware store turn-buckles.
Zanco says, "It produces a very effective sound; if you would close your eyes you would think you were listening to a genuine bass. ...It is very convenient because it has a hole cut in the side of it where Ice can carry all of the band's accessories." Moose says they would put their instruments in the hole in the side of the bass when they went from place to place.
Hardware Store Turnbuckle Tuners - Taking a look at the photo, we see that Moose's description is dead-on. Bob Ice's bass had a primitive scrolled headstock, but it sported two turnbuckles that held and tightened the strings. If you look very closely, it appears that the strings are original gut bass strings and there may be a large staple serving as a zero fret bridge.
Tailpiece and Bridge - It looks like Bob Ice's plywood bass used a conventional upright bass bridge, possibly salvaged from another bass. The tailpiece is a hinge or some piece of metal that serves as a device to tie the strings. In this photo, we can confirm these are gut strings.
The Side Hole! Yes, the waist cutaways of the bass were exposed holes, just as described! This is where the band put their accessories as they traveled from gig to gig.
I think I've found a recording!!! Bob Ice was part of the New Orleans band, The Last Straws. They recorded at least one album, "The Last Straws - FIRST!" It's definitely Bob Ice on the bass, however I'm not sure if it's the plywood bass. The photo on the album cover has him holding a conventional upright bass.
If anyone has more information on Bob Ice and his 2-string plywood bass, email me at firstname.lastname@example.org