The 1950s were a time of many health-related slogan cancels. Moe Luff's "United States Postal Slogan Cancel Catalog" Revised Ed 1975, has the following listing on page 42:

Here is a collector sent-for example from Norwalk:

So despite being used at only Norwalk/South Norwalk, it would be common due to its span of use throughout the 1950s and collector mail on the moderately high-speed International and Universal canceling machines of that era.