RAJ - if you were unfamiliar with the 5.56 x 45 mm cartridge, and did not have the box for the ammunition, you would not know it is a 5.56/.223. Although the box for this ammo, if the correct one is shown, is a mixture of commercial and military style boxes, and therefore hard to know exactly where this ammunition was destined to go once manufactured, the headstamp is a military style.
Military headstamps very often do not have the caliber designation of the cartridge on the headstamp. When the ammunition is produced for a military, or in some cases for civilian use, military headstamping regulations of the country that ordered it, or if a member of a group like NATO, the parent group’s regulations. In the case of civilian-contracts, the headstamps can be the result of designs submitted by the end-user of the ammunition, or if not specified, by the factory that makes it.
It is assumed that the country that is issuing the ammunition to its troops knows what caliber it as, as do the soldiers to whom it is issued.
In civilian ammunition, if the countries producing it follow CIP or SAAMI (CIP - European governing body for commercial ammunition specifications; SAAMI - American governing body for the specifications), than it is those two organizations that set the general guideline for what information the cartridge headstamp must contain. However, many countries and manufacturers do not comply with CIP and/or SAAMI specifications.
Obviously, never attempt to use any ammunition until you have verified the caliber (case type), its suitability for the gun you wish to use it in, or the type of loading (some loading types, such as armor piercing, tracer, incendiary, explosive, etc. are illegal for civilian possession and/or sale in some countries, or in some States within countries. Other combinations can simply be dangerous to the user.
In this instance, the box label clearly indicates that the 5.56 mm ammunition original to the box is ordinary Ball M193, and suitable for military weapons of that caliber. There are some differences between the normal military 5.56 x 45 mm NATO cartridge and commercial .223 of most commercial ammunition, although frankly, I have found them to be generally interchangeable. As always though, caution must be used.