Blue Triangular Bottle

Here is probably the best of today's findings. I am not sure if this is anything special, but the blue color is really awesome. It was rather dirty and cleaned up well. It is about 7 inches long and 4 inches wide. I really do like glass, and I admire the collections of people on CW, but I just do not understand how to get into collecting glass. It must be a real skill! It looks like this bottle has a marking with the number 3 on there somewhere. Anyone know what this is??? I would love to know. Thanks for looking!