While reading "Great Fishing Tackle Catalogs of the Golden Age", edited by Samuel Melner and Herman Kessler, Nick Lyons Books, Lyons & Burford Publishers, 1989, I found the following advertisement. This was a page from the Hardy Brothers, Ltd. catalog, 1914, pg. 111.

The following table of silk gut names and sizes is given:

Name

Refina

Fina

Regular

Padron 2nd

Padron 1st

Marana 2nd

Marana 1st

Imperial

Royal

Size, in thousands of an inch

7 to 9

11 to 13

13 to 14

14 to 16

15 to 16

16.5 to 17.5

18 to 19

18.5 to 19.5

20 to 22

The table refers to "Guaranteed pure unbleached Spanish `Selecto' gut".

Further, the advertisement states "As the largest retail importers of Spanish gut in Europe, and actual gut workers in drawing, twisting, plaiting, cast making, etc., we fear no competition either in price or quality. This will be at once apparent when our prices are considered; in doing this, it should be remembered that only the finest Spanish `Selecto' is offered. In casts and drawn gut, quality is our object. We cannot make better. We guarantee that only Spanish gut is used in our works, and that of the highest quality only."

The authors added a footnote that says "Hardy's drawn silkworm gut always had a high reputation for strength, partly because the `X' designations were one step larger than those of their competitors; thus 3X was .007 inch diameter for everyone but Hardy's. Their 3X was .008 inch diameter."