I thought I would share a little of what I know, or what little I know, about these bottles for those new to them, or at least new to the scope of variations.
It's hard to come up with a single descriptor with which to identify the type of bottle we are talking about here. Most come from Communist or former communist block countries, or countries who use firearms whose design was influenced by Russia. These bottles were most often issued with the SKS, Mosin Nagant, and the Kalashnikov group of weapons. For simplicity's sake, I will simply refer to these bottles a ComBlock bottles.

  Most American gun oil bottles have a tapered spout or closure for applying the oil straight from the bottle. At right is an M16 oil bottle.
ComBlock oil bottles held a generous amount of oil with an opening in the top large enough accommodate an oil brush like the one below.


A Chinese gun oil brush.

The most common style of Chinese oil bottle is the small plain bottle like those at left. They range in color from green to olive brown. China produces the widest variety of oil bottles.
Most ComBlock oil bottles can be broken down into the four categories below. The dual chambered bottle design allows for both oil and some type of alkaline bore solvent. Dual chambered bottles are always metal as they have to be constructed of several parts soldered together. I have yet to see a plastic dual chambered bottle. The Romanian AMD65 address this issue with two separate plastic bottles in a plastic tray. The AMD65 alkaline bottle is the only bottle I have seen that is red.
Single spout, metal or plastic.                                   Double spout, metal, round or rectangular.                           Two bottles in tray, plastic.

A dual chambered Romanian oil bottle with one side removed to reveal the partition.

Caps are nearly always stamped, but on rare occasions they are machined.

Plastic bottles can come in a rainbow of colors. Above is a small sampling.

Older caps have cork seals, newer caps, synthetic.
The metal bottles are usually some shade of silver or brass, though I have one Polish dual chambered bottle which is finished in black oxide, shown at left.

Detail from a Russian AKM poster showing
the contents of the tube style cleaning kit.

A typical tube style cleaning kit, sometimes referred to as the butt stock cleaning Kit. On most guns with wooden stocks this fits in the butt under a trap door, shown at right. Move your cursor over the image to reveal the cleaning kit.