Randall; My "Service Instruction Manual" has on the "Front Cover": "Publication Part No. 502602":
On the "Back Cover" it shows this: "ISBN 0 948207 69 8": Does that designate that it may have been printed
Aug. 69?
I don't think so. According to
https://www.isbn.org/faqs_general_questions and
https://en.wikipedia.org/wiki/International_Standard_Book_Number the "69" is the publication number while the "8" is the check digit.
But the fact it bears a ten digit ISBN would seem to indicate it was printed after 1974 (which of course doesn't necessarily mean it was updated then). I'm not certain, but I believe what you have there is a Brooklands reprint of the original factory manual.
https://www.abebooks.com/9780948207693/Triumph-Tr2-Workshop-Manual-Tr3-0948207698/plp
What does the title page say as far as edition & printing? Does it have a hard or soft cover?
Here is a scan from the 3rd edition of "Practical Hints for the Maintenance of the Triumph T.R.3", P/N 501528/2, which I believe was updated in 1957 for the introduction of the "wide mouth" TR3A model even though the wiring diagram does not show the separate rear turn signals (that were also introduced in 1957).
And one from the 2nd edition of the TR4 workshop manual, P/N 510322 updated in 1965 (although I don't think the lubricants page changed, that's the edition I have).
PS, 502602 is the TR2/3 workshop manual. It doesn't cover TR4 at all. AFAIK it was never updated after the introduction of front disc brakes (late TR3). For example, the 3rd edition says nothing about how to remove the TR3A type headlight trim rings, separate turn signals, etc. If yours has any of the material for the TR3A, I'd like to hear about it.