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Key Lock on a Shoulder Seam Bottle Mark Mystery

A while back I tried to buy a bottle that had a mold mark on it that I didn’t recognize. The mark was on the shoulder mold seam line, 90 degrees from the shoulder mold parting line seams. So it became a bottle mystery. Unfortunately or untimely I found the solution before I got this one written up. This was an early utility bottle that sold on eBay. I didn’t win the sale, also unfortunately. Now that’s three un-‘s.

Here is a picture of the mold mark that puzzled me.
keyed lock system (top right), which was called a Full-height Three Part Dip Mold

I was studying in my #3 Favorite Book “The Illustrated Guide to Collecting Bottles” by Cecil Munsey, and found the answer on page 39. There was mention of keys being used to hold mold shoulder sections on molds as far back as 24 AD and before the hinged shoulder sections. Now that perked my interest. I read on and found that early dip molds for bottles were set up with vertical lifting shoulder sections. Some hinged on two sides of the dip mold for lifting up and out to release the blown bottle for lifting it out vertically. These were often keyed in lock-up to the top of the dip mold by key slot in the side of the dip mold at the top seam match and a key on the shoulder section that locked into the dip mold keyway, producing a positive location of the shoulder sections on the dip mold. Some molds were set up with a vertical hinge pin on the side of the dip mold and side swinging shoulder sections that could be opened and closed by a mold attendant to permit opening and lifting the formed bottle out of the dip mold for empontilling and finishing the top of the bottle to the desired finish. Full-height three-part mold. [1]On page 43 there is a picture of this first keyed lock system, which was called a Full-height Three Part Dip Mold. On that same page the next picture shows the side swinging shoulder mold system, which was also called a Full-height Three Part Dip Mold. Both pictures were from Dr. Julian Talouse’s work.

I am quite sure my mystery bottle was done on the first type of mold pointed out here, although the picture does not appear to have a lock key system. Earlier dip molds had individual shoulder sections that had to be manually placed on the top of the dip mold after the parison was inserted for the blow. The method was too slow for the bottle makers and didn’t have much favor. They preferred to work with the free formed shoulder method.


Now you know, if you see this key mark on a shoulder match seam that, this was how it got there. Find one and you’ll have an old bottle.

Red Matthews [2]

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