I didn’t know when I posted (and I was too tired to work it out), but thought to keep it as it was part of the title. I’ve just checked out his mastodon again, and I think they may be Roman numerals to denote a recurring title (eg Re-Construct XLII, and Re-Construct XLIII)?

I could be completely wrong though

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You’re in luck as that seems to be a recurring theme in a lot of his work!