The years of service these pins represent is obvious, but there are many variations to be seen. I'm sure there are many more than are shown.
11 - Five year pin in sterling.
12 - Five year pin with enamel.
13 - Another five year pin with enamel. Note the difference in enamelling in the "Five Years" banner at the bottom.
14 - Ten year pin.
15 - Ten year pin.
21 - Fifteen year pin.
22 - Fifteen year pin with stone.
23 - Fifteen year pin. While it may not be obvious, this pin differs from pin 21 in that the banner at the bottom of the pin is painted or enamelled a pale blue.
24 - Twenty year pin.
25 - Twenty year pin.
31 - Thirty year pin.
32 - Forty year pin.
Fifteen year pin in original box.
Twenty year pin in original box.
Wings pin.
Long-Term Service pin. Probably a promo item.