I love and always keep my eye out for older bottles and marbles. I have stuff going back to the 1880's/90's which is old for around here. You can see the glass colors transition from a bluish green or the pinkish rose type color to clear. The only Coke bottles that I pick up now are the dark blue stubbies, as the clear is relatively common here. I have some blues bottom stamped from Montana, North Dakota etc. If I find a single old swirl marble in decent condition, I have already had a satisfying day, regardless of any coin find...........Tip: To find old bottles walk at the base of hills and look up through the brush in the leafless spring time. If you see heaps of brown rusting cans, go in and look. Sometimes all you'll see is a glint off a semi buried bottle. If you find a depression, start digging, it may have been a trash or burn pit. People used to dump their wagon loads of garbage down a hill. Your eye gets trained to see these spots quickly after a while. Another tip..... Check any shallow creeks or rivers when the water is low. Lots of bottles in water. If searching for Indian points, check a field in the morning after a rain. The wet stone glints a little in the early morning sunlight.