A grading firm will eventually appraise vintage Dungeons and Dragons modules, early supplements and maybe even box sets.
Grading these items would be a multiple in cost compared to a card, but the slabbing and grading would be worth it.
The current increased revenue may translate more RnD investment and whoever is first will have a significant advantage. I hope it is CGC.
On a side note, DA Card world took a while to begin buying all DnD items. I have no earthly idea how this is done without grading. A meta appraisal system can be more efficiently applied than a micro assessment. Staple rust, loose pages, staining, browning, creases, tears, fading, completeness and authenticity can be summed into a score, but individual preferences make this challenging without an unbiased arbiter.
Some have been awaiting this service for years. More for a short while. Enough are waiting now.