One reason there may not be a lot of rifles/guns older than the 1870's/1880's is that there really was no widespread sport hunting tradition until that time. Hunting was largely market based and people used the best tool available. The hunters of the latter 19th century really developed the traditions which we recall with nostalgia. Hunters before that period would use the latest and most efficient tools available to them, and likely have no attachment to their older "tools". I doubt that gun collecting was an issue anyone even considered during that period. Since they didn't do it, the older guns are not available for us to enjoy.