Your model came in a version with hand crank, but it would be a challenge to find one. If you do it is probably attached to another Wertheim Machine. I found a little info on it,
here is a link to the Sewalot home page.
Here is a blog post on the subject. With a bit of search you will find model number, and perhaps various other names it was sold as. As late as 1930 I'm guessing all models came with option for motor and bracket for mounting.
Here is a picture randomly roaming the web, from a now deleted sales add.
