Just drop the prefix and first number. UY227 is a 27 tube. UX171A is a 71A.
Your numbers are for old globe shaped tubes. When they changed over to "ST" the prefix was dropped. The different prefixes would indicate manufacturers. The numbers you listed are RCA.
Norm
: What is the sub. for UY227 , UX171-A , UY227 ? Cant find any on this links tube sub chart.