Im pretty sure yokes for 15 and 12 are the same. There are identical on the RCA schematics.
If you don't already have it, RCA vol. 1 Color TV service Manual (Tab Books #496)
https://picclick.com/Vintage-Tab-Boo...177180696.html
is a very important text if you want to understand all about these. .
Carl Babcoke never included a foreword like other Authors in this series BUT he must have really been listening in the service seminars RCA must have had. The troubleshooting steps for the ever-common issue of red-plate/No HV so common to RCA New Vista color TVs.