This is a Martin O Type Ukulele. I believe it to be dated pre-1930 since it has no front headstock sticker and is stamped on the back of the peg head with the Martin logo. It also has the Martin logo stamped inside the body on the back above the middle brace.
It is in pretty good shape, a little beaten up, with a few cracks and a split at the lower bout side to top connection. The finish appears that someone has done some touch up, although not a very good job.
The body is mahogany, and there is no body binding on this model. There is a black/white/black/white sound hole rosette. The fretboard and the bridge appear to be rosewood. There are 12 frets on the fingerboard. The body dimensions are 9-3/8" long, 6-3/8" at the lower bout, 4" at the waist, and 5" at the upper bout. The neck length from body to tip of headstock is 11-1/4". The neck width at the nut is 1-3/8", and 1-7/8" at the body joint.
The tuning pegs are friction type. I have taken one of them apart to show what they look like. I could not find much reference to these type of tuners on line, so I am providing this photo.
There is a small spring inside the body. The shaft is square, and the unit pulls apart once the top screw is removed. Tension is increased by tightening the screw once it is installed.
This piece will need some major reconstruction items to get it playing. The neck is loose, so it will probably come off and be reset. After the neck is off the top will be removed in order to do the necessary body repairs. A refinish is probably in order to try and fix the previous job.