Hi engee:
Back to our discussion (I took a break for dinner).
I don't subscribe to the belief that there is one definitive source for English grammar, which happens to sit on your bookshelf :)
English grammar is complex and often contradictory. Heck, grammarians can't even decide on something as simple as the correct use of the apostrophe. AmE and BrE grammar usage has evolved with different acceptable "practices".
I don't know the source of your "rule", but I suspect it could/would likely be contradicted by an equally dusty old tome on this side of the pond.
Just for fun, I googled "age of * years old" and imagine my surprise to see that 264,000,000 examples popped up.
Like I said before, I agree that "age of X years (old)" seems a bit redundant but I don't believe it to be a grammar error. I respect and admire your knowledge of English grammar engee. I'm happy to learn from you and others on this forum. But this really isn't about grammar, you obviously had an agenda engee. You wanted to discredit a native English speaker who had the temerity to hang up a shingle advertising his services in PL.