Hard saying for sure just what created this solid amber patch within the otherwise aqua CD 164. It looks like a piece of beer bottle cullet got swept into the furnace, and didn't have time to fully melt and combine with the aqua glass before hitting the mold press. Found it at a yard sale a couple of years back, being used as a flower garden ornament. **UPDATE: Paul Greaves suggested it might be the result of a hairline crack that absorbed a dark amber liquid, and upon inspection with a magnifying glass, it appears that may have been the cause. Thanks Paul Still junk in glass... just not the kind we like to find. :-)