Usually identified as a 1971 issue as they replicate that year's artwork from Rocks O' Gum, previously covered here, we'll see momentarily Gum Berries came out in 1972.
55 lids make up a set and here is a scan, courtesy of Gina at Net54, of a lid proof:
Here are a few proofs from eBay:
A box flat just sold cheap on Ebay as well:
If you look at the manufacturing information planned for the bottom of the box, you can see this was a 1972 production:
There is a 1974 Topps product catalog that shows a raspberry version of Gum Berries so I think it's possible the 72 version was a test of sorts and reused the Rocks O' Gum artwork as it was handy and of the proper configuration. Topps tested all sorts of products and materials, not just trading cards, and it appears it took them a few years to be happy with their "rocks".
Gum Berries are harder to find than Rocks O'Gum, which are among the most common of Topps issues. I suspect there was a massive find of the latter at some point as you could buy sets in groups of 9, all in plastic sheets (55 sheets with nine examples of the same card in each) at one point on eBay for a song.