Check this link, scroll down to Fletcher's post:http://recpit.prosoundweb.com/viewtopic.php?t=11174&sid=1363336f88338ae2f630fbf079c4ed70
From what I gather, in the interim period Neve were not making 1073/81, the lamination supply for the exact Lams / Bobbins dried-up. Therefore, when the cloners started Carnhill had to build a new o/p transformer to spec, but with slightly different lams and bobbins, metric sizes instead of the original that used imperial size.
Neve were not happy about one or other idiosyncracy in the re-manufactured units, and consulted their original documentation and instructed Carnhill to make adjustments.
The transformers made for Neve DO differ from what Carnhill sell to the public, but whether this difference in spec makes an appreciable audible difference would be open to debate I guess.