You might be able to find similar examples of church Sunday School "attendance award" pins for sale on the internet. Most will be new-made ones, for sale by the manufacturer or a dealer. For example, there's a bunch for sale at the following website, but the backs aren't shown:
Cross and Crown Sunday School Attendance Award Pins & Bars
I decided it would be better to search the internet for "used" ones. I searched for Ebay auctions which show the pin's back, and I found the maker's-mark that is on your pin's back. It says "Little's Cross And Crown System."
I did additional research and found only one result which tells a date for a "vintage" Sunday School attendancepin with the same makers'-mark as yours. It dates the pin as being from 1930-40.
Union Station Kansas City
Apparently, the marking saying "Little's Cross and Crown System" was used by the Christian Finance Association. It dates at least as far back as the 1913, but continued for at least 50 years, perhaps more. I do not know if it is still operating today -- but it might be. That means there's no way to know from the maker's-marking whether your Sunday School attendance-award pin was made in the 1930s or 50s or 70s, etc. Sorry, but this is the best I could do for you.
I found a long .pdf document at the following webpage, dated 1913, which says "These [Corn Club pins] may had be ordered from the Christian Finance Association, 80 Maiden Lane, New York, N.Y."
http://aurora.auburn.edu/repo/bitstream/handle/11200/1833/1019CIRC.pdf?sequence=1
For cleaning the back of excavated (dug) 20th Century brass items, I use plain ammonia (cleaner) poured into a small bowl, and soak the brass object for a minute or two, then gently scrub with a toothbrush. Do NOT let it soak for more than two minutes. (Also, be sure to rinse the object thoroughly when you're finished cleaning.) I said "dug 20th Century brass" because dug 1800s-&-earlier brass can be harmed by using pure ammonia. For those items, I dilute the ammonia 50/50 with water.
