I would highly recommend Boker for a congress pattern, I'm a congress fan and feel that Boker represents that pattern well and executes it to a degree I judge all other congress patterns to, but as Meako hinted at there's a rule you'll need to follow " German made " is sort of a loose term, what you want to look for is Solingen made, Solingen steel, if you are buying a carbon steel or C75 steel Boker it is Solingen made, stainless steel Bokers will say Solingen stainless, if it simply says stainless steel or as their currant outsourced line says high carbon stainless steel in the description 9 times out of 10, more like 10 out of 10, it's made with outsourced parts and assembled in Germany hence the "German made". With Boker to get a 100% manufactured and built knife the shield will say Solingen if the shield reads Germany it was outsourced, same goes for tang stamps, the verbiage is important to get what you want and can be tricky. Also in the past Boker has made patterns for Hen & Rooster, the reissued Russell's, J.A. Henckels and a few others. The only 100% Solingen German made congress patterns being produced at this time by Boker are the Beer Barrel Congress item # 115464BBL, Boker Carvers Congress item# 115465 with rosewood scales, you can find old new stock Bokers or slightly used ones on the auction sites but you need to know what to look for, I've seen unscrupulous sellers list new magnum or plus lines ( made in China ) as " Vintage Boker" so remember look at the shield if it says Germany it is outsourced, if it reads Solingen it is 100%, there are exceptions to the rule special additions with reissued shields that don't say anything , but the tang will read Solingen. If you find something and are not sure email me through the forum and I'll be more than happy to help assist you.
Beer Barrel congress
Carvers Congress
And the currant line of German shield outsourced, which unfortunately now have Tree Brand on the blades very misleading as before Tree Brand Classics were a sign of the quality products sort of a bait and switch IMO
As for currant Hen & Roosters and Buck Creek they are owned and distributed by Frost Cutlery so my guess is parts are outsourced and assembled in Germany
Pete