Life / Toy horse in pocket for good luck according to the Polish tradition? [7]

I have been in a serious relationship for the last four years with a Polish girl and this year was the first year that her Grandmother gave me a gift. It was for my birthday, a little plastic toy horse. She said to keep it in my pocket for good luck. I searched everywhere to see if this gesture has a greater meaning or where this custom originated but there is absolutely nothing on the internet. Anyone here have any knowledge to impart? It would be greatly appreciated as even my girlfriend (who is very connected to the culture) has no idea what this is about.