DC813 .....My dept. (M.W.C.C.) authorizes the wearing of service stripes/hash marks for years of service. I believe one mark stands for 3 years of service and the officers wear them on their long sleeve duty shirts.
I retired from B.U. after 27 years. Generally it was the us older guys who wore the hash marks. The younger guys were either "too cool" to wear them or didn't last long enough to earn then. We wore them on the left side of our long sleeve shirts as well as the same side on cruiser jackets. We who had them, generally wore leather jackets w/o the hash marks (didn't want to mess up the leather). Each hash mark was worth 5 years. So after 27, I left with 5 of them. Hope this helps. By the way this is a really nice site. It's too bad you can't get a little interaction going with the municipals. Get to know each other a little and learn to respect on another. Both jobs are more alike them different. It takes the same amounts of guts to strap on a gun and hit the bricks no matter what department you work for.
We just started, on dress uniforms and since there is a crazy turnover here, for every 3 years 1 hash mark. And there has been talk about every year after you can have 1 also but, nothing in stone. No one has made it past that anyway. None of the above is mandatory.