what it contained?

[miki4]

First World War relic (probable).
I apologize if I do not write well in English!
And thank you in advance who will help me to understand what it contained the relic consevato by my father to ricondo of my grandfather telling him to belong to the Americans during the First World War. E 'in effect a cylindrical metal top cover with 14 cm in diameter 8 cm with an inscription: "to open the lid and remove ting cut until pressvu point is directly downwards replace lid and turn sughtly press."
What my father told me he did not know precisely what never was and, originally, from the object and not having a date stamped, I wonder if it can be traced back in some way, a year of construction.
hello
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sorry I can not enter, click on the image directly address below

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