Some searching shows that they are part of Speed cooling products and their Chevy truck radiator is pretty well the same one I have from Engineered cooling products. The radiators are built in the same building but it looks lik the Entropy are probably built to order while the engineered cooling are production line.
Their web page
https://entropyrad.com/
ECP / Speed cooling page
https://ecp-radiator.com/
I'm thinking that most likely The ECP radiators are made in China while the Entropy radiators are hand made by a small highly skilled crew and you do pay the price for it. Still their radiator is in the price range of a US radiator,
The welding on my radiator while plenty solid is not what you would want on a top level show truck. Reading Entropy's about us page, theirs should be high level show quality.