Chris,
I'm probably not much help, but in the 1914 Rangliste I can't find any Oberst Winkler. There are two Oberstleutnant Winkler's, but they're both artillery and it looks to me like there's a spike on that helmet, not a kugel. Just in case he might have gotten promoted I looked at Majors, there are two of them, but one's artillery the other is a Major a. D. at a Landwehrbezirk. So thinking the handwriting might say Oberleutnant, I checked and there's only two of them listed, one is in Infanterie-Regiment Keith (1. Ober-schlesisches) Nr.2, the other is in the 1.Garde-Grenadier-Landwehr-Regiment.
On Wetsel there are only Leutnants. On Wetzel I found one Hauptmann in Landwehrbezirk VI Berlin. Just in case the name might be mispelled I looked at Wetzell, there is one Major Wetzell who is listed in two places Generalstab der Armee and III.Armeekorps Berlin.