Here is the marking on the bottle bottom. First, the "c" in McL doesn't have an underscore and the letters are aligned along their tops instead of their bottoms which is the typical embossing. Second, there is a capital L in a circle below the two digit number. What does the "L" stand for? This is the first time I have seen this particular marking on a McLaughlin bottle.

Update 11/17/12: I corresponded with several McLaughlin largeware collectors. The lack of an underscore under the "c" and the top justification of the letters (vs. bottom justification) are not unusual McLaughlin bottle markings. The one marking that is very unusual is the capital "L" in the oval, which is a marking for Latchford Glass Works-- also historically located in the Southern California area and a competitor of the McLaughlin Glass Company. There are older Mission Spring Water bottles without the "L" in the oval.