It came to former Czechoslovakia many years ago from former Soviet union. Under the name "Grusevidnyj" which is fonetic transcript from russian language and means "Pear-shaped", but for sure - fruits are not pear-shaped and no one, even in todays Russia know, why it got this name. It is hybrid with unknown origin. Most likely cross between citrus sinensis and citrus paradisi, but leaves have sometimes large wings, like papedas. In book Citrus of the World from Corsica research station it is labeled citrus paradisi.
Fruit is a size of big mandarin, very juicy, easy to peel, with soft orange flesh and very soft membranes, often seedless, taste of pulp ressembling sweet orange, but taste of the membranes is similiar to citrus paradisi.

Thanks for the information Radoslav.

Thanks for sharing... I enjoyed this post.

Very interesting variety, how hardy is it?

The color of the pulp is the same color as the golden grapefruit. - Millet (414-)

GT. as you are in Texas, you might be able to purchase a Golden Grapefruit, or perhaps some budwood, from Mr. Texas. ( 414-)

Are there two different varieties of Golden grapefruit ? One seedless & one full of seeds.

http://www.harveysgroves.com/shop-Golden-Grapefruit-13.cfm

http://www.fbmg.com/CommunityEducation/FruitSales/Fruit2007/FruitPhotosCitrus.htm

This variety came to Czechoslovakia from research station in Sotchi, many years ago as a gift from horticulturist Fyodor Mikhailovich Zorin, there are many citrus varieties in our collections from that man.
Very nice article (in english) about citrus "tree of Friendship" in Sotchi:
http://www.sochi-international.ru/pages.php?id=1&pid=27&ppid=65&lang=eng

To Lemandarangequatelo: I will check the hardiness.

To Millet: Internal colour resembling Golden grapefruit, but fruit is much smaller than grapefruit. Grusevidnyj has yellow-orange color of rind, when fully ripe, with orange dots.

Waoo! A 77years old PT with 635 grafts!
I think JoeReal is going to get sick!

Very cool.

Millet,

thank you very much for your hint! MrTexas, being very nice, already gave me budwood of GG that I grafted on multiple seedlings. I'm trying to be patient while waiting for the first crop... hopefully, in a year or two. I just thought that a seedless GG would be excellent as we like the fruit very much!

Laaz,

thank you very much for the link! It would be excellent to find budwood from what Harveys' get their fruits.

Actually, I have another novice question: assuming that Golden Grapefruit does not cross-polinate with other cultivars, could it produce seedless fruits?

Radoslav,

thank you for the link! A very interesting story indeed!

There are 60 citrus trees around the World, grafted with budwood from the original PT tree in Sotchi as a symbol of unity and peace. One of them is in Long Beach California : http://www.waymarking.com/waymarks/WM53GV_Sochi_Friendship_Tree_Long_Beach_CA_USA

Text on Monument/Memorial Sign or Plaque in California:

Friendship Tree
To Cultivate a Garden Of Unity and
Brotherhood Among The Peoples Of The
World, This Wild Lemon Tree Was Planted
in 1992 By The Long Beach - Sochi Sister
City Committee. This Tree Carries A
Graft Of The Original Friendship
Tree in Sochi, Russia.

I think mentioned grapefruit might be similar to the C. Paradisi 'Sotchi' from the Oscar tintori nursery.