I wrote a blog post that addresses two related topics: coins in D&D (and similar games) and the method of advancement I am calling found advancement.
I’ve been thinking and writing about similar stuff lately and seeing musings about coin hoards more generally in the Classic space. It’s nice to see a growing interest in looking at the treasure and experience.
I enjoy the note on roman coinage weight, and the list of narrative concerns that coins bring. For my home game (using slot encumbrance with 1K GP purses, so it’s not so important) I’ve adopted a similar weight calculation and the explanation is that old Imperial Coinage is smaller and more pure then the debased mintings of the Resurgent Kingdoms. Haven’t worked in some of the other social concerns, but I may have to even if the setting is fairly lawless.
I’m firmly in the XP=GP (or more abstractly value) for ludomechanical reasons, despite any ludonarrative risks, but agree that if one is going to use milestone advancement a clear (and I’d hope presented early in campaign) list of sites to visit (lost holds to recover, ancient shrines to cleanse etc), artifacts or perhaps even specific monsters/threats to defeat is the best option.
You may also want to look at Marcia’s Blog and her recent thoughts on using a more granular and abstracted “treasure” system for ummm… treasure (something that I think was a Goblinpunch idea from a few years ago). She’s been doing a lot of stuff on OD&D lately that’s well worth a read (plus the Lacanian analysis is very fun).
I’ve been thinking about this for a while, too, but your and Marcia’s posts are probably what nudged me to write the thoughts.
XP=GP works for ludomechanical reasons, as you say. One can call my “found advancement” idea a species of milestone, but by the same token, GP are milestones, too, just scattered ones that take a while to accumulate into a moment of substantive advancement.