I found "Two Bit" and received the following reply to my question:
I do have to disagree that the tang marking has anything to do with export of rifles to Britain. The tang stamp style on your rifle, with or without the small "MOD 1892" stamped across the tang, is found between SN 476000 and 502000. Roughly 25,000 rifles This corresponds to production from 1909 for the Model 1892. The earlier guns with the style do not have any MOD 1892 added to the tang whereas the later examples in this range do have it. Those early gun are indeed lacking any Model designation on them. The majority of the rifle in this range are sporting rifles in 25-20 WCF caliber. I have catalogued right at 200 rifles with this tang stamp style and not a single one has any foreign proof stamps! I know Madis claims the tang style was used for export guns but the data does not support that claim.
It is interesting to note also that during 1909 this identical tang stamp style was begun to be used on the Model 1890 slide action .22 caliber rifles. Those rifles already had the Model designation being applied to the barrel so there were no guns produced without model designations. This style was used until 1915 for the Model 1890's. Certainly Winchester did not intend to solely export 6 years worth of 1890 production.
It is my belief that the use of this tang stamp style on the Model 1892 rifles was a production error. I will be the first to admit that 25,000 rifles with an "error" is a bit hard to believe but the export idea does not make sense either.
