However, I find it very hard to believe that they would have continued to use the WT triangle mark all the way up to 1969 (when Armstrong was purchased by Kerr), as stated in some sources.
I have never seen any bottles with the WT mark that appear to date after the 1940s, or maybe the early 1950s at the latest.
In 1838, at which time the glassworks was then known as the “Phoenix Glass Works”, Captain John M. Shortly afterward, the firm name became Scattergood & Whitall after the retirement of Haverstick.
Whitall entered the business in partnership with G. Franklin Whitall, John’s brother, then joined the firm in 1845.
W-T is especially well-known for the production of tremendous quantities of prescription bottles, blown for hundreds of local druggists/pharmacies across the country, embossed with their names and addresses using interchangeable slug plates inserted into the mold. Less commonly-seen are examples found in a beautiful rich teal green glass, as well as cobalt blue.
( https://openlibrary.org/books/OL25302802M/Simpson_Springs_Station ) which can be read online (page 83 on that pdf file).
Wang Film Productions (formerly known as Cuckoo's Nest Studio) is a Taiwanese studio founded in 1978 by former Hanna-Barbera employee James Wang as a means for the company to outsource their animation to (when the technique was still relatively uncommon at the time).
Since its founding, Wang has worked with and/or for several companies like Warner Bros., Disney, Nelvana, Klasky-Csupo, Film Roman, Universal, Kennedy Cartoons, Toon City and Studio Pierrot (among others).
Many of their pharmacy bottles have a letter or letters embossed (along with the “W. CO”) on the base which were typically mold identification marks (not date codes).
Note: some of these earlier clear glass bottles may turn a pale amethyst color if subjected to long exposure to sunlight.