50-300 is fine.
If we do not state a definite upper limit then we run into a Sorites paradox, where n+1 is as good as n and hence we arbitrarily increase.
Wouldn't it make those 50-300 limited run coins more costly? If they are rare, these coins will surely be auctioned in future which shouldn't happen, since theymos has said that he offers these anniversary coins to only to few specific members based on certain criteria. Also, it would be good if those members were selected who has really contributed to the forum such as MODS, devs of epochtalk (probably just an idea), donators and other reputed guys roaming here. This shouldn't be handed over based on so called merit criteria since not all top merit receivers know about collectibles and their uniqueness actually.If we do not state a definite upper limit then we run into a Sorites paradox, where n+1 is as good as n and hence we arbitrarily increase.
I like the sound of this. We could have a design and print done rather quickly, and be ready to ship before the anniversary.
Your notes were always of the best quality right from the newly made 10 year Bitcoin note and the community would love to see how you bring out the note if it was for the forum anniversary. 
Until now I haven't even joined any of the many giveaways because I don't want to dox myself, but I might have to reconsider for this anniversary edition.
You could trust collectors like MJ, they are a lot more trustworthy than any one here and would help in even reshipping them to your address. I guess MJ has a separate warehouse (The Mantis warehouse) for his collections. 