Flak 36 (37mm) anti-aircraft gun

I photographed this German anti-aircraft gun during the 2010 Thunder Over Michigan show in Detroit. I had determined the gun was a 3.7 cm type, but I called on the Hyperscale nation to help narrow it down. Two answers came back as either the Flak 36 or earlier Flak 18. Because most of the earlier weapons were updated, I will stand by the Flak 36 label until informed otherwise.

Flak 36

Willows Run airfield; Detroit 2010