Originally published 3/11/11, 10:22 am.
See Vayiqra 2:1 and Rashi
Rashi asks -
Q: Why is "Shemen" said twice?
A: Because the 2nd & 3rd drops are kosher for m'nachot unlike the shemen for the m'norah which may come only from the first drop.
Now using this we can understand and answer the Question -
Why would the Kohein Gadol seal a "pach shemen"?
A. Because he needed to set aside M'norah oil away from M'nachot oil.
Mystery solved! Unless the 2 oils appear differently to the naked eye.