Thanks to all who have responded both on and off list. My
understanding of these artifacts has been considerably extended by the
replies I've already received.
The consensus seems to be that glazed (and sometimes unglazed)
tubular pipes were manufactured by local companies during the last half
of the 19th century (perhaps even several decades earlier in a few
places) and were widely available by the 1880s (considerably earlier
than I had believed). The key variable identified by those responding
seems to be the start up date for local manufacturers of brick and tile.
Thanks again to all.
Chris Murphy