The Enell postcards in my collection are printed on three different papers told by the looks of the backside of the postcard. I guess that also gives an idea of the years of printing. The three different types of backsides are: EKC, Kodak and a third not known to me. Below you find scans of the three types.

Type 1 -EKC | Type 2-Kodak | Type 3 - unknown

My used postcards have cancellation dates as follows:
Type 1: all unfortunately unused;
Type 2: 1949-58; 13 postcards, average of the 13 is between 1951-52.
Type 3: 1956-58; 6 postcards, average of the 6 is 1957!

This does not give the full truth but at least it gives a hint on printing dates. According to internet sources the EKC stamp box was used before the Kodak one. I therefore tend to believe that the original (very first) print of the series was made on EKC paper in the late 1940's. Later prints were done using Kodak papers (starting obviously at least 1949), and the "newest" prints were made on papers called type 3 by me (second half of the 1950's).

Postcard issued by Tushita, Duisburg, Germany