Remington Model 1900s are a simplified, cheaper, version of the Model 1894, built on the same patents -- No. 528,507 and No. 528,508 both granted Oct. 30, 1894. The Model 1900s were all K-Grades, with E added to the designation if the gun had ejectors and D if it had Damascus barrels -- K-, KE-, KD-, or KED-Grades. The K- and KE-Grades had Remington Steel barrels. The Model 1900s had a snap-on/off forearm and their serial numbers were in the 300,000 range, often preceded with a stock letter Q. Model 1894s had serial numbers in the 100,000 range, often preceeded by a stock letter P. Remington only used the terms "Model 1894" and "Model 1900" in the parts lists. In the the Remington Arms Co. retail catalogues, the guns were all "Remington Hammerless Double Barrel Shotguns" and just differentiated by grade. Both the K-grades and the A- to EEO-Grades were built concurrantly from 1900 to 1910. The $750 list price Remington Special was introduced in the 1902 Remington Arms Co. catalogue and remained through 1909. Remington Special serial numbers were in the 400,000 range.
You need to check out Charles G. Semmer's book "Remington Double Shotguns." It is available from the author 7885 Cyd Drive, Denver, CO 80221, for $60 plus $5 shipping and handling. It is invaluable if you are going to shoot, invest, collect or play in the Remington double gun field. Remington supplied a number of different pattern Damascus barrels on these old doubles. A picture of their salesmans sample of the various styles of Damascus available is shown on page 275 of Semmer's book.
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.
By the end of the first decade of the 20th Century, Remington saw that the future laid with their John M. Browning designed Remington Autoloading Gun (later known as the Model 11) and their John D. Pederson designed Remington Repeating Shotgun (later known as the Model 10). So, they concluded a deal with Norvell-Shapleigh Hardware Co. of StLouis, for their entire inventory of break-action shotguns in inventory and in process, on February 3, 1910. There must have been a lot of guns involved, because the records show 3206 Model 1894s, and 16435 Model 1900s shipped in 1910. The 1909 Remington Arms Co. catalogue was the last one to include the doubles, and there was a version of the 1909 catalogue that only had the Remington Autoloading Shotgun, the Remington Repeating Shotgun, and the Autoloading Repeating Rifle.