Seeking Urethane covered ball

I buy used but nice and clean balls from a local vendor. He displays a sample of all balls on a big board. All balls are cut in half so interior is shown. He shows many, many balls, many probably now discontinued from active new sales. If i want to buy a urethane covered ball would you say that i should look for a ball with 3 or more layers? Would a ball with only a cover and total solid interior be 'non urethane'?  How else could i judge whether the ball has a urethane cover besides the number of interior layers? Cost of balls varies from 20, 30 or 50 balls for US $13, depending on market. 

Yeah, i know urethane is the name of a type of plastic material with characteristics similar to balata, the former superior and soft ball covering.  The alternative to urethane seems to be surlyn, also a kind of plastic stuff but harder, more rigid or tougher than urethane.  But by looking only,  can someone determine if the ball is covered with urethane or surlyn?  Could even an 'expert' tell by feel only, never seeing the brand or model?  The consensus is among folks who know is that hardly anyone can discern brands of red wine without seeing the label. Blind testings of red wines among even New Yorkers reveals nothing about the cost of the wine, said to determine quality.  Could be the same for golf balls. If you could not see the name on the ball, all balls would be alike.

But to refer to your comment, iacas, that urethane may cover any ball, regardless of number of layers, whether 2 or 5. seems to indicate that looking at balls cut in half won't tell me if the cover is urethane.  But i strongly suspect that balls with 3 or more layers would more likely be urethane covered as such balls are more expensive. 

Is there any 'one piece' ball with no separate covering material? Take warm white plastic, form it into a round ball, press some dimples, write "Titleast", cool, package and play.