I know I recall this subject being mentioned before and there was suggestion that an "R" stamped under the guard bow might mean that the stock was a factory replacement. Here is ferther evidence to support that fact.
This example is 30" Damascus GH number 84960, made in 1894.
The forend is no doubt original to the gun. However the buttstock, which fits perfectly, is of a later style. Main ques such as the style of the comb and grip, rounded bottom of the checkering pattern, and the buttplate without spur and domed buttplate screws are features found on stocks made in the 1920's and later.
Also, there is a noticable color and finish difference between the stock and forend.
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When the trigger guard was moved out of the way, the matching serial number to the gun is found along with the grade "2" stamp and also a large "R".
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I had to break this gun down for cleaning and when I did, I found evidence of it being a factory replaced stock. The inletting in the head of the stock was cut for the earlier top lever mechanism, not the post-1910 design. But the cuts for hammer clearance was of the later shallow style. When I removed the hammers, I found that the rear "horns" that were on earlier hammers had been removed as to convert them to the later style.
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Also, the later style "flat" safety spring and corresponding jacket were installed in the gun. However, the original safety button was retained.
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Oddly enough, the 1910 combination bolt and wear plate was not installed in the gun. Which was, to my understanding, a common free of charge job done to any gun returned to the factory after 1910.