Remington stamped the barrels of the Model 1889, 1894 and 1900 with the results of a standard load shot at a 30" circle at 40 yards.
My question is: Did any other manufactures use a similar system?

I guess no one knows

Maybe others are less willing to embarrass themselves mc

I'll observe that I've never seen choke % marks on a Smith, Parker, Baker, Tobin, Crescent, or Ithaca barrel - and of those only Ithaca had the 0-4 choke code, and I don't know when that started.

The U.S. makers DID mark the % on the hang tag, as did Remington, and there are a couple of examples here about a 1/3 down
https://docs.google.com/document/d/1F2sQuPm05IE4VWYYnCkvuXmYEzQoWd_SQgaAfUOZEFU/edit

Of the Parker Bros. hang-tags I've managed to save pictures of, up into the 223xxx range they are marked with pellet counts. By the 232xxx range they are stamped or marked with choke designations -- Full, Mod, Imp Cyl, etc. Similarly early A.H. Fox Gun Co. hang tags have pellet counts and later ones choke designations. I haven't observed any makes other than Remington Arms Co. marking pellet counts on the guns.

The only Three-Barrel Gun Co. hang-tag I've observed had the pellet counts, as does the only Syracuse Arms Co. tag I've got a picture of.

So it appears that Hunter Arms got lazy some time between this 1920 Field with the numbers, and this 1925 Trap with only a %

Picture below of an early style 12 gauge Fox with the original hang and pellet count, SN 19823.

Interesting to note the tag says "EJECTOR" but it's an extractor gun.

And the tag is as crispy minty like the gun.