Has anyone ever noted the similarities between the Homer Brooke's Patent 133.1 (left) and the Chicago Insulating Company 135 (right)? Consider the following:

1. Similar color: Chicago Blue vs. Brooke's Blue. 2. Lack of square shoulder between inner base rim and beginning of the pinhole. The inner profile of both is sloped rather than squared off, as with the early swirl-threaded insulators. Manufacturer(s) apparently didn't use the Dec. 19, 1871 Hemingray-patented process. 3. Similar vintage? Both are embossed with 1883 patent dates (see also http://www.nia.org/timeline/1880.htm). 4. Similar glass. Both are typically solid, chunky, thick-walled, often filled with junk, steam, bubbles, carbon. Similar 'feel' to the glass. 5. Unidentified maker(s) of both.

That's the possibility/likelihood that these guys were produced by the same manufacturer?