You said in your post that the star said 53, but it's actually 58. If that was just a typo, then it seems like if your coin says Una Libre Grande instead of Una Grande Libre, you might have the good one.
Spain, 1957 (58 star), 50 Pesetas, KM#788, metal-copper nickel, mintage-21,471,000. If it's the common type: grade/value VF20-$0.75 XF40-$1.25 MS60-$4.75 MS63-$6.50 If it's the rarer of this type: grade/value F-$150.00 VF-$275.00 XF-$400.00 MS60-$700.00 MS63-$1,000.00 not sure which is yours yet ? grade ? rim damage ? F-VF
If you click on the link provided above (Post #5) you'll notice that the expensive coin has the letters "BA" replacing the star on the left side of the reverse. The coin with 58 stamped on the star has a mintage of 21,471,000 while the one stamped BA has an estimated mintage of 43,000.
This site should help: https://www.ngccoin.com/price-guide...-788-1957-58-195771-cuid-1082942-duid-1555586 It appears the one with "UNA LIBRE GRANDE" on the edge is more valuable than the coin with "UNA GRANDE LIBRE" edge lettering.