This set reaches well back into the 1700's, so I believe. Beyond that I can't comment, other than to speculate.

I have taken a closer look at the pictures that I have got, alerted by the extremely
different length of the lower drone sections : I believe that these pipes could have
been assembled from two different sets. First of all there are two types of beads on
drones and stocks : 1 (bead) - 6 (combing) - 1 - 6 ...and 1 - 10/11 - 1 - 10/11...
The tenors are very well made and look very much like ca. 1820 Donald MacDonald
(shape mounts, beaded drone tops, 1 - 6 - 1 - 6), but the bass drone is different,with
smaller mounts and more combing between the beads. The top mount of the lower section
does not fit and is of a different shape, and the drone top section with its cord holders
does not match (and is not a patch to) the tenors. Its ivory ring is of a different shape, too. The stocks have different beading and ferrules, one of the tenor stocks has a much longer one. The ferrules seem to be both ivory and bone. All this has to be verified and the pictures are not good enough to tell all the truth. But I doubt that such differences in style would be original to the set. The other one I bought seems to be completely original, though with slightly less combing on the stocks (1 - 10 - 1 - 10 on the drones and ca. 1 - 9/8 - 1 - 9/8 on the stocks) alternating with the same narrow beads.
If this is true both sets would obviously date from the same period, and would most likely
have been assembled in Scotland, before the owner emigrated.
Unknown # 41