I happen to have these grapes here in India with me, no one seems to know the name of this grape.
It has got a thick skin and thick gelatinous pulp.
Looks like Bangalore Blue, except your sample is seedless.
That is commonly grown in India.
Grapes in the species Vitis labrusca, or crossed with them have the slip-skin characteristic where the skin detaches easily.
The black-purple colour, with seedless characteristic and oval shape correspond with the Sharad Seedless variety, found in Maharashtra state. You might look to see if they come in possibly large bunches, another characteristic of the vine.