To go with this (posting here because it isn't an OTL map, strictly speaking), I thought I'd illustrate just how malapportioned this map is by making a complement map of what Berlin and Brandenburg, probably the most malapportioned region next to the Rhineland, would look like with roughly equal constituency sizes. I based this on 1910 census data, with population figures cited in the 1920 Greater Berlin Act used for subdivisions of the city of Berlin itself as it stood pre-1920 as I couldn't find any other data for that. For a start, while I can sort of believe the original apportionment in 1866 was fair according to the standards of the time, by 1910, Berlin/Brandenburg was short of several seats compared to what they ought to have by a Hare calculation. Whereas in actuality Berlin had six seats and Brandenburg 20, according to their populations, Berlin should've had 12 (fully twice the number they had!) and Brandenburg 24. If Brandenburg wasn't that dangerously off in pure number of seats, the actual population of each individual one tells a different story. The smallest constituency was Ostprignitz (coterminous with the Landkreis of the same name) with 64,901 inhabitants, while the largest by far was the constituency covering Teltow and Beeskow-Storckow (the southern Berlin suburbs plus a hefty chunk of countryside for good measure) with 1,314,576 inhabitants. Yes, really. A twenty-to-one margin. It got particularly egregious after 1900 as more and more cities became kreisfrei (administratively independent from the Landkreise that formed the definitions of the constituencies), and yet nothing was changed regarding the actual electoral boundaries. So, a few things became clear: there needed to be more constituencies created in suburban Berlin, but more than that, there were also too many rural seats for good measure. I set a 2:1 ratio as the minimum, which is ridiculously generous by today's (Western) standards but would probably have been in line with expectations at the time. Most of the rural constituencies in Bezirk Potsdam fit the bill, so all I did there was merge the two Prignitz districts together and merge Oberbarnim with whatever would be left of Niederbarnim (the district containing Berlin's northern suburbs). In Bezirk Frankfurt, I shifted the Cottbus seat to the north by replacing Kreis Spremberg with Kreis Lübben, moving Spremberg to the Sorau-Forst seat (which brought it over the minimum quota), then split Crossen-Züllichau-Schwiebus between Guben and Sternberg and similarly split Landsberg-Soldin between Königsberg (Neumark) and Arnswalde-Friedeberg. This actually left it with one seat more than its Hare entitlement (8 rather than 7), but I decided that probably wouldn't be inconsistent with actual practice and decided to make up for it by making larger constituencies in suburban Berlin. Speaking of which, I immediately noticed that Schöneberg almost exactly fit the quota, so that became a seat to itself. Charlottenburg initially seemed about the right size to split down the middle, but that left Spandau without a logical way to get up to quota, so keeping in mind the need to have larger seats here anyway, I took off the western third of Charlottenburg (the bits west and north of the Ringbahn, as I decided) and merged it with Spandau, leaving the rest as its own seat. A bit crude, but it's basically how the present-day Bundestag seats work. Wilmersdorf fit the quota with Grunewald, Schmargendorf and Friedenau (basically the small bits around it) added on, so I didn't look the gift horse in the mouth. I initially experimented with lopping off a third of Neukölln's population onto a Treptow-Köpenick seat, but a combination of the increasing ridiculousness of that and the awkward half-seat left in the north by a similar Lichtenberg-Weißensee combination meant I abandoned that idea and left Neukölln unchanged, straddling the upper limit of acceptable size. Instead I merged Lichtenberg and Treptow - an awkward combination to say the least, but it made the numbers add up. That pretty much left two big seats, one in the north and one in the south, each one made up of roughly the urbanised area (going partly off populations and partly off what areas gained a "Berlin-" before their official names from 1912), and of course finally the remainders of the Teltow-Beeskow and Barnim seats. (Sorry for the word salad, fellow non-Germans, but it's very hard to explain this without it) What of Berlin itself, you ask? Well, when Greater Berlin was created in 1920, it was divided into six Bezirke (districts or boroughs - a further 14 of them were created from areas annexed to the city then), each one of roughly equal size. These were Mitte, Tiergarten, Wedding, Prenzlauer Tor (later Prenzlauer Berg), Friedrichshain and Hallesches Tor (later Kreuzberg). You can imagine how useful this was to me - I just split each one in half (roughly, according to my eyeball measurements), and done. This ironically meant keeping two of six Berlin seats almost unchanged, and shifting a third only slightly to the southeast, while the remaining three were redivided into nine new ones.