Dinner at mine or yours?

Solution 1:

I don't think it's an anachronism - I think it's relatively new. This is an example of an omission-gap conflation and a retro-intrusion parallelization followed by a pronomial generalization. (No, ha-ha, not really - I just made that up because I can't remember the real name for what that process is called, but it happens all the time in language.)

The previous form we're used to is: "my place or yours". But actually what's happening even here with "yours" is that "place" (digs, crib, cottage, castle, flat, house, whatever you want to name it) is already omitted. What is implied is "my place or your place". "Your place" conflates to just "yours". This happens in language shift for many different reasons, like efficiency, intimacy, regionalism, etc.

In the example above, the more current form of "mine" is changed to parallel "yours": the conflation of "yours" syntactically has a leftward influence and causes the same conflation of "my place" into "mine".

Then, the use of "mine" takes on its own meaningfulness and independence of usage, and as in David G's comment "we went back to mine..." Where the use of "mine" referring to "my place" no longer needs the context of "yours" or "your place". It morphs into its own stand-alone from possessive pronoun liberated into full noun-ness.

In American usage, I've only heard it in colloquial phrases like, "Don't worry, I'll get mines." Meaning, "I'll get what's owed to me." The form "mines" includes a final "s" either because it parallels (or mimics, or experiences intrusion - I can't remember, and I can't find the term for it...sorry) the final "s" in "yours" or because "mine" has already become nounified and the "s" indicates the plural...

What would be cool to find out, if anyone knows, what forms or production of possessives in other languages (not English) may have been an influence in your different regions - and how human geography shifts the usage... or even better, we could ask Anthony Horowitz...