The Tonk Brothers started in Chicago in 1893 as a music publisher and musical instrument distributor and though the company continued using the name, the last Tonk Brother had left the company by 1923. 

Though they were not Ukulele manufacturers themselves, being based in Chicago in the 20's meant they had a lot of dealings with the makers like Lyon & Healy, Regal and JR Stewart who did, and like the New York distributors of the time they owned a number of the brand names that they distributed and had makers put these onto instrument for them. They also brought all of Lyon & Healy brand names in 1928 when L&H decided to concentrate on making Harps. In addition to the L&H Brands - Washburn, American Conservatory and the like, (though I have only ever seen Tonk use Washburn as a brand name), I have seen Tonk used Tonk Hawaiian, Tonk American, Deeptone, Columbian, (nothing to do with the British Banjoleles), Beau-Ideal, Sterling, (Hafner & Sutphin may also have used this brand name?), Mapeliene and La Venecia, sometimes with a TB Co. as well. Unfortunately in looking through old Tonk Bros catalogues there are also a lot of Ukuleles and Banjoleles that appear to be unbranded too. 

In the 1930 Tonk Catalogue it has as item 108 a "Bass Ukulele" however if you look at the size they set for their Tenor, (22 inch total length which would be today's Concert scale), and that most of the Ukuleles are described as Concert with no Soprano or Standard Ukuleles mentioned this shows more to do with the National Association of Musical Instrument and Accessories Manufacturers and their "Standard Approved" scale definitions and the fact that this didn't go up to the 17in scale Ukuleles of makers like Martin and Gibson than any lost larger scale.