If you could happen across a lost item or treasure from history, which one would you want? Myself, I’d want the Masamume sword along with the 14 others turned over to a still unidentified US soldier at the end of WWII.
Holy Grail:
The tablet containing Commandments 11-15.
Eric Clapton’s Beano 'burst, the '59 Les Paul he used to record the “Beano” album with John Mayall and the Bluesbreakers and led to the Clapton is God graffiti. Stolen in '66 I think.
I’m not a huge fan, but it would have huge value and a 59 burst would be fun to have! It’s whereabouts are rumored to be known, in the hands of a collector with a huge number of bursts.
Is the Library of Alexandria too much to ask for?
The intact Antikytheria Mechanism.
The movie Remodeling Her Husband from 1920. It’s the only film Lillian Gish ever directed, and it starred her sister Dorothy Gish. The libretto, or “script,” in so much as silent films had them, was written by Dorothy Parker, who also composed the intertitles. I want soooooooo much to see that movie.
Statue of Selket from Tut’s tomb.
The lost reel from Woodstock showing Pete Townshend smacking Abbie Hoffman with his guitar.
No, so I call dibs. You’ll have to think of something else now.
I’ll take the Colossus of Rhodes.
It would look very good in my living room. 
The Ark of the Covenant, with tablets inside.
The original deck of Tarot cards.
Yes. I mean, there are various modern reconstructions of it, and I do believe they’ve probably worked out the function and purpose to within a smallish margin of error, but still, it would be lovely to see a working original example.
I’d also sort of like to be able to recover King John’s lost treasure, but I am not sure I believe it was really lost in the way reported.
The first set of tablets Moses brought down from the mountain. I want to see if they match the commandments recorded.
As for things I think actually exist it’d be cool to have some genuine viking war kit, as it is there’s very little archaeological evidence for what they wore in battle before starting to import arms and armor.
The Amber Room. I haven’t redecorated in ages.
And the missing Apollo 11 tapes.
Mention of the Amber Room reminds me that I’d love to at least see, if not actually have (oh, what the heck, have–it would look better in my yard that a garden gnome) the silver tree of Karakorum.
Marlowe’s complete works. English culture is much poorer without them.
I just want my original Privateer game back.