These are found with an amazing variety of headstocks, Dobro, Ward, Regal, Alhambra and Old Kraftsman to name just a few.
All were made under license from National-Dobro by Regal of Chicago, from about 1935 to 1941 and, I believe that if you could order a minimum of 100 they would put 'your' name on the headstock. Since most instruments were sold through mail order, or catalogues, a substantial number of the big companies such as Montgomery-Ward (Ward on the headstock) or Spiegel (Old Kraftsman on the headstock) ordered sufficient quantities to have their own models.
The adverts below came from the Tonk Bros mail order catalogue
3 different headstocks and shapes!
The model 32 with slotted headstock & the model 62 with solid headstock
Note that the 'price' is the model number!
The Dobro lite, this is a late one with solid headstock and tuner coverplates.