I think an >1oz International Letter is as good as use as any for those $2 Inverted Jenny stamps! : r/stamps

4806c Inverted Jenny $2 stamp Imperf Single (Upper Left position) No Die Cut

Rare US stamp 'Inverted Jenny' sells for record $2M

Inverted Jenny - Wikipedia

Another upright Jenny find; USPS says 32 reported

I think an >1oz International Letter is as good as use as any for those $2 Inverted Jenny stamps! : r/stamps

Semi-official airmails

Why a single 'Inverted Jenny' stamp sold for $2 million at auction : NPR

4806a - 2013 $2 Inverted Jenny, single from pane - Mystic Stamp Company

Inverted Jenny, Full Pane of 6 x $2 Postage Stamps, USA 2013, Scott 4806 : Office Products

The art director for this souvenir sheet was Antonio Alcalá.

Lot of 2 Inverted Jenny Stamps Souvenir Sheet of 6 $2 stamps

The Inverted Jenny: The Stamp That Sold for $2 Million - The New York Times

New report brings upright Jenny Invert tally count to 43

Inverted Jenny, Full Pane of 6 x $2 Postage Stamps, USA 2013, Scott 4806 : Office Products