Unidentified marker signs

[US-Subs]

I don't know when the US went to the standard triangle markers for mines, so no idea what was used previously. Do any of you "gear" guys recognize these? Can you tell me their purpose and approximate date of use? Thanks.

 

[kiwieod]

i would say pre ww2 as the triangle type sign features in ww2 us army manuals.ive seen this set before,its fairly common although its the only US item ive ever seen with US ARMY on it,usually its just "US".