The partnerships between those dates are (according to Bell):
Cornfoot, Carr & Patton, 1834–1847
Carr & Patton, 1847–1848
John Carr, 1848–c1850
John Carr & Co, c1850–1854
John Carr & Son (note singular), 1854–1861
The plaques produced in the earlier partnerships would likely have been of higher quality than those produced from 1861 onwards. So perhaps Carr's finest plaques remain unattributed. Carr & Patton also took over the Phoenix Pottery, Ouseburn, in 1847. Bell writes that their partnership was apparently dissolved a year later, with John Carr continuing at the Low Lights Pottery and John Patton at the Phoenix Pottery. Separating their wares of the 1850s might be difficult, unless we can show that transfer plates continued to be used by the later Carr partnerships.
The engraving below of the ship Marco Polo appeared in The Illustrated London News in 1853. And yet the plaque, attributed to John Carr's Low Lights pottery, was likely made in the 1860s. So did one of the earlier Carr partnerships make plaques using the same transfer during the 1850s?
Look at the plaques below and their details, particularly the flags (click to enlarge and to move from one photo to another). The first two have a flag on the first mast, the third doesn't. The first two have seagulls flying around the masts, the third doesn't. Through tiny flaws in the engraving, I am certain the first two come from the same transfer plate. The third plaque is a low quality variation, produced in much smaller numbers. The transfer is over-glaze, and I suspect it was produced later than the other two plaques. Its dimensions are within a couple of millimetres of the first plaque.
Click on the details of the two plaques below. Remember, every dot and line of shading was engraved by hand. These two plaques are clearly from the same transfer plate. As we'd expect, the transfer of 1860's plaque on the right shows evidence of wear.