Thank you Kin, Craig, mdcarma and josphy for your comments and advice.
I wasn't sure which way to approach the request from the man in the UK. My sense was that a hi-rez file was not the way to go and I was concerned about losing control over the use of "Eyes left."
I did agree to a limited use of " Fun at the Fountain." another one of my 10 Florentine postcards which have been circulating in Florence since 2001. http://flickr.com/photos/lesged/58551901/in/set-72157594433862983/
It was a similar situation where a third party passed on a postcard to the one who wanted to use it. In that case, it was the assistant to the art director/manager of a Dutch company that sponsors 4 seasonal Children's Fairs. She vacationed in Florence saw my postcards on display and showed it to her woman boss suggesting that they use it for the invitation for their summer or fall's fair.
We came to an agreement and they sent a letter, not a contract, stating its sole purpose was for a one time use. They paid a very fair price, enough to buy the the same camera I took all the photos in the "Italian Period 1958-1959," i.e. Leica IIIf w/ coated 2/50 Summitar in top shape with original case and a Leitz multi-finder. It also included in the double kit was a beauty of a Bessa-R with 2.5/28 CV Skopar. Mike Elek made an affordable package price for both cameras and I was pleased as punch to make that deal which the Dutch company's payment covered.
BTW, the boy in "Fun at the Fountain" is our elder son Marc, whose photo with Claudia taken in Copenhagen in 1955, was shown last week in the Classical Camera forum thread "Found 1955 negative of fave photo"
Thanks again for all your responses.