Google "lunker potato"

I got a couple of responses, including a thread from several years ago

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" Purple Viking

Truly a beautiful potato, with deep purple skin dappled with pink splashes and stripes. Bright white and creamy-good, the flesh bakes or mashes perfectly. This variety produces what we call "lunkers:" large oversize potatoes, so plant close (8"-10") to control size. "

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"Kennebec Poatoes i.e. The Lunker Spud
Posted on August 20, 2009 by onestraw

Moose Tubers bills the Kennebec as a potato capable of throwing some "lunkers". It is also known for being fairly simple to grow and an easy potato to cook with -good for everything from frying to baking to boiling. Easy to grow and easy to cook -plus it produces big spuds? IÂm sold.

I am less than 15% of the way into my Kennebec patch, but I can personally confirm the "Lunker" claim. In 60#Âs of harvest potatoes this evening, I had 8 spuds over 1# each and 1 monster that broke 2#! Also, we have a new Record Holder in the 1 Plant Harvest contest:
4 lbs 13 oz. from one Kennebec Plant. Top Left is 1# 1oz Top Right is 1# 13 oz!"

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And this Article:

http://www.halcyon.com/tmend/giants.htm

Have fun

Catherine

Here is a link that might be useful: Lunker Potatoes