204 and 205 have a slide stop, and are in 22LR only.
Both are sometimes called 'American Models'
204 has standard grips w/thumb rest. 205 adjustable grips.
206 & 207 are 'International Model' pistols. So called high speed actions, they have 'Olympia' in the center of the slide on the right side. & Hammerli International on the left. Adjustable grips, bbl weights, muzzle break, ect.
Cal 22short & 22LR
The remaining 2 models,,200, and 203 are near identicle.
The 200 was the first post war target model to appear and was to be as close of a copy of the 1936 Olympia modal as possible.
There's also a model 300 that is supposed to be about the same as or identicle as the 200, but I'm unable to ID the differences.
Available in both 22short and 22lr.,,22LR is more common.
The 200 thumb rest grips but could be had w/ adj grips as I understand it,
The 230 came with adjustable grips standard.
The 200 could be had with and w/o a list of bbl weights, different rear and front sights, muzzle break ect.
The 203 came w/a standard set of 2 bbl weights, muzzle break.
Rear sight options were available also.
Left side Slide markings on the early production 200 :
Walther 'Banner' Lenzburg Hammerli
or
Lenzburg Hammerli Switzerland Olympia-Pistole