Yep, the Mouse was a unit insignoa in the Kondor Legion, but don't know its origins. Many of the Luftwaffe unit badges, shields etc were based on the area, or town, where the unit was originally formed, often using the towns badge, or coat of arms, or that of the area. For instance, the Grunherz badge signified the Green Heart of Germany, after the area where it's original Kommandeur originated, the well known shield and cross of Jessau was another, and the Bear of Berlin another, and so on. The shields such as that used by JG26, with the Gothic 'S' were normally 'Honour' titles, in this case Schlageter, a rather unsavoury Nazi activist, killed in a street fight in the 1930s.