Below left is the transfer as it appears on my Garrison plaque, and on the right as it appears on the pink round-cornered plaque.
Another factor, I'd not previously considered, is that copper plates were sometimes re-engraved. Appendix III (Baker) states: Because copper is a relatively soft metal the transfer plates were subject to a good deal of wear and required repair. Engraved lines which had become too shallow to hold the required amount of ink were retouched and the plates themselves, which had gradually become curved due to being squeezed between the plate rollers, were flattened out. I wonder whether the diagonal hatching in the clouds to the left of the ship (on the second plaque), might be such an attempt to improve the quality of the image.
According to Baker, the Garrison Pottery sold its copper transfer plates when it closed (1865). One such plate was presented to the Sunderland Museum by a member of the Ball family in 1963, engraved with the name 'Dixon, Phillips & Co'. Baker writes 'this copper plate appears to have been passed into the hands of Moore's or Scott's (possibly both) and finally to Ball Brothers'.
None of that really helps with our attribution. What we can say with some certainty is that the round-cornered Gauntlet plaque post dates 1865. The first Garrison Gauntlet plaques were likely produced just after 1853 when the ship was launched.