From Declaration Mark: Citrofortunella Vulc, Made in EU, by Waterdrinker, 2006.
Searching web I found nothing.

I found that plant in a local store yesterday:
30 cm tall, formed in cordon like style, growing from own roots!?
A big lemon like fruit, 9 cm * 7 cm.
A lot of flowers, opening these days.
Photos:
1. Plant

2. Flower buds


How hardy could it be ? -5 C ?

Plant repoted, fruit consumed

Comparing with an ordinary lemon:
-------------------------------------
Cuted halves color: slightly more orange.
Smell: remainds me on Meyer.
Slices: 9 (ordinary lemon had 10).
Seeds: 9, smaller, greenish.
Taste: less acidic.
---------------------------------
Overall impression: Excelent.

With the purple tinge to the flowers I would say it is some type of Lemon.

If the seeds have greenish coloration to the cotyledons then one of the parents has to be a kumquat. Plus, the "Fortunella" in the name is also a give away. Citrofortunella must be a made up name for marketing purpose. Could be a lemon kumquat cross.

Millet
Dr. Justina L. Ford MD
1871-1952

Based on the fruit shape & size:
Which lemon variety could be a parent?

Wild guessing, based on that lemon & kumquat hardiness:
What Vulc (vulcano?) hardiness could be expected?

Thank you for participating.

From the leaves it looks like a Meyer with the serrated edges. It may also be a grafted tree and the branch the lemon is on is from the rootstock. It is hard to tell with that leaf in the way.

About Meyer Lemon being one of the parents Laaz is probably correct on two accounts. 1. The leaf shape and 2. The flesh having an orange cast and taste. Tthe word Volc perhaps is referring to the understock Volkamertana.

Millet
Dr. Justina L. Ford MD
1871- 1952

Following "Meyer" suggestion I find this:
"Citrus X Lemonquat - Citrus x 'Meyer' X Fortunella margarita 'Nagami' - Shrub - If acclimated, hardy to 10º F. "
at http://www.floresflowers.com/taxa/Rutaceae.html
Unfortunately no other info available.

Inspecting "fruit branch":
Tip of the branch has flower bud, that is the highest one far left on Plant photo.
Leafs on the fruited branch looks the same as others.
Vulc has a small thorns, 2-3 mm. I see no thorns on the fruited branch.

http://ccpp.ucr.edu/variety/319.html

http://www.hort.purdue.edu/newcrop/morton/lemon.html#Varieties

Citrus X Lemonquat - Citrus x 'Meyer' X Fortunella margarita 'Nagami'

First, the formula you printed above is not complete. You can't just have the single word "citrus." Citrus what? The category "citrus" encompasses a lot of varieties. Second, if the understock is indeed Volkamertana, you would not see small thorns, because the Volkamertana portion would be the understock. The understock would never show thorns no water what variety of under stock it was.

Millet
Dr. Justina L. Ford MD
1871- 1952

I tracked down the real manufacturer of this plant, it is "Viveiros do Foral": http://www.viv-foral.com/company.php?lang=en&file=profile
There I got as contact Jean-philippe from "Green Synergy" http://www.green-synergy.com/ who according the EAN CODE identifies the name of the citrus as "citrus lemon meyer" and later according to the plant photos confirms it.

So, I have two Meyers now!
1st is mature plant and visualy differs from this new.
Thorns are much bigger, leafs are more elongated, flower buds are more elongated and with different top, rootstock is Poncirus Trifoliata...
I hope that, with a time, fruits of new Meyer will taste as good as fruits from old one.
BTW:
What if my old Meyer is not "Improved"? Can I identify that?

Ivica, if your tree is nothing more than an Meyer Lemon, then I wonder what is the meaning of all this.........fortunella Vulc?
Millet

Millet,
That is what I would like to know too.

So far it's seems that I'm cheated on two ways:
1. Last Friday, when I buy that plant, I was in a search for something "special". Reason why I buy that plant was it's name (never heard of) and the fruit size (never saw fruit that big, 7*9 cm).
2. For the price I payed for that plant (40 cm tall when unwided) I could buy TWO ImprovedMeyers 1 m (or more) tall, even in that nursery.

I talked with them this morning, they (MBM d.o.o.) are importers of that plant, and checking their EAN code I find that the name behind that EAN code is Citrofortunella indeed.

Plant name behind the real manufacturer's (ViveirosForal) EAN code is "citrus lemon meyer".

All this people which I have contacted by phone (ViveirosForal-Portugal, GreenSynergy-Netherland, MBM-Croatia) appeared sincere to me.

This could point to WATERDRINKER (exporter) as the one who messed with the name of the plant but I have no contact with them...
Seems that WATERDRINKER is mainly in a pots business...
I'm not going to continue with this 'investigation'.

I sent e-mail to Viveiros do Foral to inform them about all this.
--- case closed for me ---
I like my new citrus anyway

Ivica, you can't go wrong purchasing a citrus tree.
Millet