Reproduction Coca Cola Syrup Line Etched Glasses

I have two Coca Cola Glasses.   They are 3 7/8 inches high, with a 2 3/4 inch diameter at the top.  The base has a diameter of 1 3/4 inches.  The wording says "Drink Coca-Cola."   There is also a  syrup line about one inch from the bottom.  The writing and syrup line are a greyish white (not bright white) and have a rough feel to them unlike the smooth painted bright white words I have on some other coke glasses.  There is no writing on the back side of the glasses. There is a shield mark on the bottom.  When viewed through the glass a capital "F" is visible.  When viewed from the bottom, the "F" is backwards.  I could not get a very good picture of the mark, but you can just barely see the shield in the last two pictures.  The first is looking at the mark from the outside; and the last picture is a view looking into the glass at the shield. I understand that reproduction glasses like this were made in the 1970's or 80's.  How can I tell if what I have is early 1900's or 1970's or 80's?  These are in excellent condition with no chips, cracks, etc.   Thanks so much for any help on this. 

MWH