You might also be able to compare features to manufacturer’s catalog data. If any degree of reliability is expected, it may be a boat-anchor candidate.
A rough approximation of hottest spot rise could be calculated from oil temperatures, and average winding rise per IEEE C57.12.90. It is required by IEEE Std. C57.12.00 that the hottest spot temperature not exceed 80 oC. Other useful reference could be the IEEE/ANSI Std.C57.91
[sub]ADDITIONAL REFERENCES:
IEEE C57.12.00 Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating
Transformers.
ANSI/IEEE C57.12.90 Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating
Transformers.
IEEE/ANSI Std.C57.91 “Guide for Loading Mineral Oil-Immersed Transformers”.[/sub]