This is part of the GEO-CLUE series. See GC217T7 for more details.
The container has information you will need to find the final cache in the series. The information is inside an envelope in the cache. The envelope contains either 1) a clue card identifying a suspect, weapon or room NOT involved in the murder or 2) a code.
You need to keep track of all the clues to find the Accusation cache.
Oh, the shark, babe, has such teeth, dear
And it shows them pearly white
Just a JACKKNIFE has old MacHeath, babe
And he keeps it … ah … out of sight.
Have fun and be safe.
You can validate your puzzle solution with certitude.