Welbars are Welsummers with the gene for barring (from a cross to a barred rock many generations ago). They are autosexing in the same way as Legbars and Rhodebars. All of these autosexing breeds were created by adding barring to an existing breed so that the male chicks will have a white head spot.
 
Being Welsummers at heart, you would expect them to lay dark colored eggs, and they do. Being autosexing, you would expect them to be 100% sexable at hatch, and they are.
 
Their only drawback is that they are quite rare. They have existed in the UK since the 1940's, but were never common. As far as I know, our flock is one of only 2 or 3 in the entire US. We created these using the same genetic recipe as the original UK Welbars. The process is well documented , but takes at least 4 generations of careful crossing and selection of the resulting chicks.

Welbars have another unique trait, they are literally only one gene different from Welsummers, so you can cross a Welbar roo to pure Welsummer pullets to get more Welbar pullets. 100% of the pullets from this cross will be full blooded Welbars. The cockerels from this cross should not be used because they only have one gene for barring and their chicks will not be autosexing, and not all will be barred, but if you breed your new Welbar pullets back to their father, you will get 100% autosexing Welbar chicks. This makes a Welbar cockerel quite valuable if you wish to create Welbars and already have a flock of Welsummers.

UPDATE !!
Greenfire Farms just announced that they have imported Welbars from the UK and will be selling chicks in 2017. Rumored price is $99 per chick. But you can get them now and have laying pullets when others are just getting chicks.

We are calling these "Heltzel line Welbars" to distinguish them from the "Greenfire Farms line" that should be available in 2017. Since they have released very little information abouth their birds, I don't know how they will compare. Because these are only F5 from an outcross to a Barred Rock, these are still showing some variability, including some with slightly crooked toes, but the newness of this line adds to the robustness of the birds since they don't suffer from any inbreeding depression.
Welbar hen
Egg comparison (left to right)
Welbar
Welsummer
Copper Marans
Day old Welbar pair (female on left)
Welbar chicks
Group of 8 males and 5 females
Can you identify the females?
Welbar Cockerel