From my point of view, and from how I read/interpret the English text, I don't agree that there is a
real distinction in Simonides word's between his description of the manuscript base material (i.e. parchment) and his description of the inscriptions (i.e. on the parchment base material). There's a possible distinction, but is it simply part of the overall description of the parchment tacked on at the end of the sentence/paragraph (context) - rounding up his thought. This is subjective IMO. (
See "This...it bore...and also...much injured by time". Note particularly the "It" in "it bore the inscription..."!) "Much injured by time", separated by a comma, is a subjective add on that could be interpreted either way.
But what's definitely NOT in Simonides word's is an "only" in "and also a short discourse [comma] , much injured by time". The "only" is Chris Pintos spin on the text. The "much injured by time" is part of the overall wider context of the parchment base material's description. To my thinking "much injured by time" antecedents/connects with the near context of "prepared...many centuries ago" as a continuation of the overall description of the parchment.
But, then there's the added complication of how accurate is the English translation (including the comma) from Simonides Greek original? And I think (from memory) there's two English translations/versions of this letter which need to be compared together. But where's the original Greek letter? Is it in someone's archives somewhere? How well does it reflect the original letter's Greek grammar?