I create a variable font exported it and installed it on my mac. A few months later I’ve had to make some tweaks to the font so tried to save it as {fontname}v2.
When I come to install it, it is saying that the font is a duplicate.
How do I export this as a new font that fontbook won’t recognize as a duplicate?
Can you show the dialog that telos you it is a duplicate? What exactly does it say? And did you make sure your new version has not been installed multiple times yet?
What exactly is the change you made to the name? What was the name before and what was it after?
It does seem like that in the Clara Legal-Mac font there might be a name value of Clara Legal. Earlier, you mentioned renaming with adding v2 to the name, but that is not shown anywhere in your examples. If changing the Family Name to something entirely new doesn’t work, then there’s a parameter somewhere likely still set to Clara Legal.
In addition to looking through the parameters in the Font, Master, and Exports tabs of Font Info (Command-I), you could look at the name table of the compiled font file to see where that name is set via FontTableViewer or DTL OTMaster, both linked on the Tools page or ttx (part of fontTools; also included in the AFDKO tools).
If it has anything to do with the font itself, then take a look inside the compiled OTF with FontTableViewer or OTMaster. You can compare both the original and the new version side by side.
Can you really exclude you did not already install the OTF once before? Can you open the triangle to display the individual fonts, and reveal them in Finder.