You'll have to reconnoitre ebay and dealers for that info.
General appraisal from the link given prior
For collectors of postmarks however, there is a challenge, which is to collect all 11 parish bootheel marks on this issue, and this is something of a quest.
It is generally accepted that with most of the bootheel marks on these De La Rue Britannia's, the available set runs from 2 to 11 and excludes the numeral 1 bootheel of St Michael. This is because the numeral 1 was used at the main GPO in Bridgetown and due to the volumes of mail going through this office they adopted newer cancellers much earlier than the outlying parishes.
So, the GPO numeral 1 bootheel is known to have been in daily use between 1863 and 1878 and with this stamp, SG74 being issued in 1875 there is, in theory, a three year window of overlap. In practice, however, they are hard to find.