Oliver Ditson Ukuleles
Most Oliver Ditson's ukuleles, their wooden ukuleles at least, were made by Martin.
As well as selling exactly the same models as Martin, Ditson used a design not featured on Martin ukuleles: the dreadnought. This uke had a less shallow dip in the middle of the body. This is supposed to give the uke more of a bass sound.
The markings on Oliver Ditson ukes vary a great deal. They may refer to Martin, Ditson or both. Even if no reference is made to Martin at all, if it looks like a Martin, it will be.
Martin weren't the only ones to make ukes for Ditson. For example, Musicguymic has this Ditson ukulele which was most likely made by Nunes.