I can not say I have ever seen a production pistol pac in an aluminum or silver case, (i am in no way saying they were never made)The older ones were the brown case with different color interior linings and the outer rim was aluminum. The newer ones were the large blue denim looking outside with the foam specifically cut on the interior.
If you know where the pistol was made these are the years.
1971 - 1992 Monson, MA
1992 - 1995 Palmer, MA
1997 - Present Norwich, NY
Dave