To answer your question of exactly what are they. These are sutures for closing internal incisions and wounds, not on the surface of the body. They are catgut, which is actually strands of connective tissue from the small intestine of sheep, and they are chromic in that they are treated with chromic acid. This allows them to retain their strength for 2-3 weeks before being absorbed by body fluids. They do not need to be removed. Boilable means they can be included in surgical packs of instruments and towels and then autoclaved without being damaged. Some suture packaging is non-boilable. They are sterile and ready to use when the glass vial is broken. The fluid is a methyl alcohol derivitive. These do not have a needle attached.
This a very common size, and was used a lot in hospitals, but not as much in aid stations or clearing stations. Very period and authentic--a great find. By the way, Ethicon is still a major suture supplier and still makes 2-0 chromic gut. It is now packaged with a needle attached, and the package is a plastic pouch instead of a glass vial.