can't identify this silver oriental medallion

My father acquired (in either China or Japan) while in the military.  I have not had success identifying the text via online translators; therefore I have no idea what this is or its possible value.

…very small: 20mm x 20mm; appears to be silver

Thank you in advance for any insights and assistance from members. 

I believe it gives the date.

Reading right to left

大正元年

The first year of Taisho (thus 1912)

九月十三日

The 9th month 13th day (thus September 13)

On the other side, again, reading right to left

青山XX場

Which reads Green Mountain (two characters I can not read) Place.

From trying to guess the missing Kanji, I get the impression this has to do with a burial location.

Maybe?  https://www.britannica.com/biography/Nogi-Maresuke

Nice.

The date is a match and he was buried in Aoyama Reien (Green Mountain Cemetery) per https://en.wikipedia.org/wiki/Nogi_Maresuke.

Thank you for your lightning fast insightful feedback.  I now have some direction to investigate further.