The Model 3 was in production from 1910 to 1913 and the slide legend should read Zella-St Blasii. The combining of the twin cities of Zella -St Blasii and Mehlis into Zella-Mehlis was done in 1919 with the Fifth Variation of the Model 4. The Model 4 was in production From 1910 until 1928 .Close to 275,000 thousand Model 4 were made with 75,00 for the military. The Model 4 remained in use after the war with the Bavarian Police. Based on the description and the slide markings it appears you have a civilian Model 4 manufactured in 1926 to 1928. for information , the Model 4 is listed at 450 in exc, 375 in very good,300 in good, 200 in fair, 150 in poor. However! Any firearm that relates to WWII is appreciating in value rapidly. You have a valued heirloom from what is called the "Greatest Generation". Pass it on to your heirs. Hope that helps