When designing the reprints of the nice triangular stamps of C10, Defend World Peace 2d series, the otherwise brutal postal authority was less brutal this time: the differences between originals and reprints are clear. And they make a difference regarding value: Originals will sell for around 70 dollar mint/35 used, reprints for around 15-20 dollar mint/3 dollar used.
Reprints have a different perforation: 14, against 12.5 with the reprints. With a somewhat trained eye pictures should be enough to confirm if it's a reprint or an original. But there is more: There is a minute Chinese marking in the form of a character in the reprint-design:
400 & 1000 stamps: In a berry of the olive branch left: 3d berry from the right (lower berry)
800 stamp: This stamp has a slightly different design, with no olive branch. You can find the marking in the right branch, in the 2d, lower, leaf from the left.
Used stamps: Reprints have almost always a light CTO-cancellation in one corner, originals have large, dark, smudgy cancellations.
As is usual in the trading of Chinese stamps, intentional fraud and unintentional misidentification is rife! Lots of reprint-sets are sold as originals. Beware!

Nice set of reprints of these triangular stamps.

Secret marking in the reprint of the 400 and 1000 stamp: in the 3d berry from the right (the lower berry).

Secret marking in the reprint of the 800 stamp: in the 2d leaf from the left (the lower leaf)

Part of a sheet: Would be great to own a whole sheet: Beautiful!