Yes I know I wrote OP (open pollinated) but I just copied the titles I had and included the OP.... (I know it's redundant for heirlooms)
I have tried to find a reference for Mémé Beauce but they are all in French because of the locality in Québec.
This is the only reference I found in English: Canadian Heirlooms: Questions - Growing Tomatoes Forum - GardenWeb
The nursery guy told me that if I kept only of flower (the top one) on this plant, the fruit can grow to 1Kg (2lbs) as per the mention on the link above.
French references allude to the story that the seeds were found when an old house was reclaimed by a carpenter. The Beauce is one of the founding regions of the NewWorld (Québec).
My seeds won't be useful next year because the plants I bought are planted close together and will cross pollinate so Mémé Beauce seeds may not hold authentic to the next generation. I purchase many tomatoes this year to try them to decide on a few next year. I will collect seeds and see what new cross pollinated plants come out. Who knows maybe I will create my own line!! (joke)
I should not get credit for these seeds. If you want the reference, I can PM you the person's e-mail addy. Luckily the growers you mentioned are in Canada. (I know for a fact that shipping plant material from Canada to USA is a very difficult task due to the new terrorism laws on imports so this guy may not have a license to ship and I do not know who can)