Interesting questions... I’m dividing my thoughts in two… First comment, re: groupings of references…
Overall, my references seem to fall into four categories: “this coin,” “these dies,” this general
type (i.e., same designs and legends), and variants & comparanda (“
cf.,” “
var.”). A few coins get all those, but for most the first isn’t available, and often not the second either. Sometimes it’s worth including a reference to comparison coins, sometimes not. Occasionally a variant or comparanda are all I can find.
I do think “
cf.” or “
var.” is an explicit acknowledgement that the referenced coin or
type is somewhat different. That doesn’t make it not “real” (I didn’t interpret the original comment as intending that, really). It’s just an acknowledgment that a fully satisfactory or adequate reference is lacking (or at least not that one).
If a specific coin has been published in an appropriate outlet, of course, it’s
good to cite it (as “this coin” or “this coin illustrated”). If not, it's best to cite a coin of the same dies. But that's not always possible either.
There can’t be a strict rule for “how close” a reference must be, since we have many categories of varying
precision (any/all of which may be
accurate), and they change over time.
I’ve used my Archaic
Herakles Hekte to discuss the “categorization” process before (
https://www.forumancientcoins.com/gallery/displayimage.php?pid=174786). It “used to be” a
BMC Ionia 7-11, or
Babelon 18 or
Pozzi 2373-5 (all as
Ionia, Erythrai). If lucky, one might even be able to cite a die match for one of these. Almost a century later, there were a few new options but nothing
had fundamentally changed:
SNG von Aulock 1942 (see also
Supp. 7891),
SNG Kayhan 737-8,
Boston MFA 1806-7 (also all Erythrai).
Then, in 2020, everything changed.
Fischer-Bossert reassigned the
mint from Erythrai (
Ionia) to Herakleia (
Bithynia). More importantly for this comment, he published an extensive die corpus for the series. Mine was Group 2, No. 10 (V 5’’/R 9; this coin illustrated). It was the only example of its die combination (and possibly for either die).
Overnight, we went from perhaps 1 or 2 dozen “
types” of these Hektes, to at least 173 different
types (and over 215 dies), across 14 Groups.
This coin went from being "common" to "unique." Of course, the
rarity only changed in the sense that we
had a shakeup of categories. But the shakeup reveals a process that's always there.
https://www.academia.edu/45579782/There’s no single correct answer for which reference to use. (But there are certainly wrong ones!) It’s up to the purposes and preferences of the cataloger to decide which levels of precision to use. Is it enough to give a reference that covers all the
Herakles Hektes from this
mint (
BMC 7-11)? Or from the same period (
Fischer-Bossert Group 2)? Specific die pair (No. 10)?
Now that
Fischer-Bossert is available, though, and I am citing it, I have begun to put “
cf.” or “
var.” in front of some of the others. If I weren’t also citing the more precise (i.e., die-level) reference, and just
had von Aulock,
Kayhan, and BMFA, I would not add “
cf.” They’re not incorrect references (aside from the
mint location); but they are no longer consistent with the die-level categories given by
Fischer-Bossert. Different collectors would deal with that issue in different ways; I might find other solutions better than what I have now. My point is just that neither the categories
nor their interpretations are fixed.
