Levi Strauss 1873-1973

Old denim was woven on 28" wide finished width off of Whitin and early Draper Northrop looms, so when a company states weight, you must do some extra division to make a present-day determination of the actual weight in the manner in which we measure today.

7oz = 9oz per square yard

8oz = 10.286oz per square yard

9oz = 11.57oz per square yard

However, even more importantly, sanforization was not invented until the 1920's, although some textile mills practiced their own finishing, more akin to decating, or with some solution mixture of ammonia aqueous, so you must take into account the shrinkage of these fabrics, which were unsanforized.

9oz shrank to roughly 13.5oz per square yard, or roughly 14.8%, just as an example.  This has been proven through fabric analysis on some of Mike Harris' early fabrics.

This element of denim construction has been severely overlooked by many companies attempting accurate reproductions of their garments.  This has led to the outpouring of poor information related to historical accuracy, and diluted the afficionado knowledge pool with claims that aren't true.

Even further, the way in which cloths for work garments, and many other categories of cloth for that matter, were denoted in terms of weight was by the yards linear to the pound.  In early 1900's header and ticket books, cloth sample books, and even handbooks on industrial fabrics, denim weight ranges from 1.4 to 3.5

1.4 = 14.69oz unsanforized, after shrink 16.89oz per square yard

3.5 = 5.88oz unsanforized, after shrink 6.75oz per square yard

It is also to note the following:

The first pants Jacob Davis made were of natural duck sail, a heavy canvas weave that was likely natural, unbleached cotton, and, based on the era, likely had flecks of boll and stem in it, which was probably quite beautiful.  This is proven in a court case against A.B. Elfelt for patent infringment, during which he was required to issue a testimony relating to the dates and particulars of his patentable invention.  

Amoskeag could not obtain synthetic indigo in the entire year of 1915, due to German embargo WWI-related, and likely had to stop production of XX cloth for Levis.  Simultaneously, White Oak Cotton Mill and Proximity Mill were producing denims, owned by Bavarian-Germans, and they only had to shut down one month, the month of August in 1915, due to embargo.  In 1913, Levi Strauss began ordering denim from their mills, and by 1916, stopped making mention of Amoskeag in their catalogs.  It was likely this that led them to experiment with logwood dye, which lacked colorfastness, yet was still purchased by Levi Strauss, who implored its use in their "Olympic Brand" line of garments.  By 1917, White Oak Cotton Mill became the exclusive supplier of XX denim, which was still 9oz, unsanforized, in the old measurements that would need conversion to present day numbers.

 

I hope that answer helps satisfy your question.  

Greetings from Greensboro, NC.