Spanish Olives

Hi,

Not sure if this is the right place to ask this but I hope someone can assist...

I have a couple of local Spanish Tapas bars near me and they both serve the most amazing little green olives. I can only explain them as tasting beefy or meaty... I asked in both places for the recipe for the brine or marinade but they would not give it to me... I suspect they come like this as both places are not linked and taste exactly the same in both places. Plus I questioned one of the waiters and he said they come in large tins.... I have tried and failed many times to deconstruct the brine and I initially thought maybe it was some sort of anchovy brine as they have that meaty savoury umami taste to them... So i bought some manzanilla olives fresh and went about trying everything... Including anchovy brine but to no avail... They almost taste like beef stock or marmite, vegemite but not as salty...

Any help would be great...