That can would hold 5 gallons of petroleum product. It would usually sit on the side or in the back of a tank wagon that held various bulk products. It could just travel in a wagon or a pickup. It might hold a specialty fuel or oil. That can is post 1900. Early cans had no ribs/flutes, next were horizontal ribs. Later cans had the vertical ribs. That tag indicates that it was approved for sales in those states. Inside the top of the neck should be a brass tag that says something like "5 gallons to this point", with an arrow. I would vaguely say from the teens to the 30's for a date. My research indicates that these were not painted at all. I have some that are not painted. They are soda blasted, which gives a super smooth finish compared to sandblasting. In general I believe that is a fair price for that can with the company name. Some would argue higher, some lower. It is, of course, yours to paint or not paint to your liking.
Thanks for all of this info, Stu.
I've seen plenty of Sunoco, Sinclair and SOCONY versions of this can. I've never come across a Cities Service version so I grabbed it for what the seller was willing to cut it loose. This can will have a nice soda blasting in the spring. I'd rather keep it original finish rather than slop paint on it.