Projected (in the plane of the sky) and LoS velocities at the age of Cas A derived from models W15-2-cw-IIb-HD (left panel), W15-IIb-sh-HD-1eta (center panel) and W15-IIb-sh-HD-1eta-az (right panel). The solid blue line in each panel is the best-fit semicircle to the data from the models; the dashed blue line shows the semicircle but artificially scaling the velocities to match the value of v_R inferred from Cas A observations; the dashed red line is the best-fit semicircle to actual data of Cas A derived by Milisavljevic & Fesen (2013).