Remington Hammerless Doubles -- Two patents were issued on the same day, October 30, 1894. No. 528,507 pertaining to the milling of the frame was granted to R. C. Fay of Ilion, New York, assignor to the Remington Arms Company of same place; and No. 528,508 pertaining to the automatic ejectors, to R.C. Fay and G.E. Humphreys of Ilion, New York, assignor to the Remington Arms Company of same place.
If the gun is absolutely plain with no engraving, just "Remington Arms Co." stamped on the side of the frame it is an A-grade if a Model 1894. Model 1894 serial numbers were in the 100,000 range and often preceded by a P a Remington stock letter. Also perfectly plain was the lower priced Model 1900 with serial numbers in the 300,000 range, and often a stock letter of Q. These were also known as the K-grade.
A Model 1894 B-grade had just a bit of borderline engraving. As the grades went up C-, D-, and E-grade the engraving became more extensive, the stock wood and checkering finer, and the overall workmanship better. There is normally a grade letter stamped on the left side watertable, or on "bridge-frame guns" (usually 103,500 and lower serial numbers) on the bridge. Also, if you remove the trigger guard, the grade letter is often stamped in the wood after the serial number.
If a Remington Model 1894 is fitted with automatic ejectors the the written grade designation has a letter E added to it and if it has Remington Steel barrels an R or Ordnance Steel Barrels an O -- AE-grade (A-grade with ejectors and the regular Damascus barrels), AER-grade (A-grade with ejectors and Remington Steel barrels), BO-grade (B-grade with Ordnance Steel barrels) or CEO-grade (C-grade with ejectors and Ordnance Steel barrels). I’ve never seen these extra letters stamped on the gun’s watertable. In the Model 1900s things are reversed. Remington must have considered their Remington Steel barrels standard and appended a D if the gun was equipped with 2-blade Damascus barrels -- KD-grade or KED-grade. "Ordnance Steel" is normally stamped on the top of the barrels on AO-/AEO- and BO-/BEO-Grade Remington doubles and engraved on higher grades.
Remington Arms Co. stamped the actual pellet counts of their test patterns on the rear barrel lug of their Model 1889 hammer doubles and their Model 1894 and 1900 hammerless doubles. If the number is three digits, that is the count, if the number is two digits a leading 3 is implied. From surviving hang-tags we know the standard load they used to target 12-gauge guns was 1 1/4 ounces of #8 going 511 pellets to the load. My 12-gauge KE-Grade Model 1900 is stamped 33 on the left and 24 on the right. That would be 333/511 = 65% left and 324/511 = 64% right, or about improved modified in both barrels. The chokes measure .027" in both barrels of that gun.
Here is a pretty good look at original Remington case colors on a DEO-Grade Remington Hammerless Double.
As a general rule, early on trigger guards and top levers were case hardened like the frames and as a general rule later they are nitre blued, but this doesn't seem to be a hard and fast rule either way.