Once designated as V2. Diameter about 16-20m, regular shape, depth about 8m, on the border of the range of V2 shooting from Bory Tucholskie about 320km (in the final period even 380km). The closest fall described on forums is Soltysy 20km to the north. For 5500km/h it is 13 seconds. Here there were Germans, 50% Poles and Nazi rigor so rather few reports. But I am not an expert. I will ask on forums.