Ammunition box. Does anyone know what model this is?

[Brazilian Collector]

Hi everybody.
I have this ammunition box, but i do not know this model is?
I have another one, with the same dimensions, manufactured by CBC (Companhia Brasileira de Cartuchos), made for storing .38 caliber ammunition, but I also have no idea of these model.
I saw somewhere that it was a box of ammunition for 240 .30 caliber cartridges, but I don't have confirmation.

 

[Linkman]

I have a similar size ammunition box and the photos. show its additional length compared with a green M19A1.

The embossed manufacturer data on the hinge end identifies it as a M61.

Of general interest is the filling data stencilled (yellow) on the side of the box... 5.56 x 45 rounds for British issue (see Government warning label), in 1966.
Web sources state that 5.56 x 45mm ammunition first used in US military M16 in 1963 (issued first to air force, then army) and, in the late sixties, the 5.56x45mm round was introduced for the first time in British service - the cartridge being used by the Royal Marines together with the American M16A1 rifle. The M16 rifle did not replace the 7.62 x 51 L1A1 service rifle and was only used in small numbers. I acquired the box in 2025 because of this intriguing marking and have only seen one other example like it for sale since.

I hope that helps.