Purpeller
The CoI minister (or his curate) made the quarterly copies so the handwriting is often be the same, differences are in the hand for the signatures (or X mark) of the bride, groom and witnesses and whether the entry number is handwritten or pre-printed.
For the Grangegorman (Dublin) example ones in <reply 20>, marriage entry 13, the brown faded page is scanned from the RCB holdings and written on the marriage day 31 Oct 1866, the other the true copy of it made 7 Apr 1867.
That minister has not been the promptest in sending his copies, is now into quarter 2 he should have sent eg 7 Jan 1867 for the preceeding 3 months. Both were written by Henry Hogan per his certification at the bottom of the quarterly copy.
The next entry in the RCB parish register [#14] is 27 Jan 1867, with 4 very different hands apparent in the signatures, and was performed by Wm Martin. By co-incidence he makes the quarterly copy (for Jan to March) on 4 Jun 1867, two thirds into the next quarter, but has a least sent on separate page and not combined with the Apr-Jun ones (sent 19th July) thereby complicating the volume filing, quarterly surname indexing and page numbering by the clerks in Dublin.
The next pages:
https://churchrecords.irishgenealogy.ie/churchrecords/display-pdf.jsp?pdfName=d-511-3-2-008https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1867/11486/8221828.pdfhttps://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1867/11496/8226907.pdfEdit: also the difference of just 2 marriages to a page on the parish/RCB vs 4 on the certified copy. Can see the bound book stitching and edges of the hardback cover in entries 15 & 16 of the churchrecords link; it had 50 pages & 100 entries then they start a new volume 511-3-3-001