near as i can tell, he used a stirn concealed vest camera.

http://camera-wiki.org/wiki/Stirn_Concealed_Vest_Camera

round film plate. no cassette, just round emulsified glass. six-exposure 14cm or four-exposure 17cm depending on model. exposure is allegedly adjustable somehow, but i'm not sure of the mechanism. plate loads into an internal frame with masks, advanced by the center dial, not sure how masks align.

many more of his photos and some images of the camera and exposed plates here

https://www.exibartstreet.com/news/19th-century-street-photo...