Here's one I found on the internet....should give you an idea of what to write:

http://career-advice.monster.com/resumes-cover-letters/cover-letter-samples/sample-letter-of-recommendation/article.aspx

Start off by explaining the "relationship" between you (how and when you met, why he hired you). Then, hit on the highlights of what happened when working together. And close out by reiterating if it was you (the former boss in this case) why you'd hire your worker all over again if you hadn't retired.

One thing to be aware of is that many word processing programs will store information about the original author when the document is created. So if the recommendation letter is going to be sent electronically, it might come through listing you as the original author, in which case the jig will be up. Of course, read over the letter more carefully than your quick post above. Threatening to "spear" someone, doesn't make for a good recommendation. :-)

Furthermore be careful to maintain the correct third person voice, it would be easy to slip and write, 'I also managed the XYZ account'

Content-wise this link has some useful info for recommendation letters in general:
http://jobsearch.about.com/od/employment-references/fl/how-to-write-a-letter-of-recommendation.htm

Perhaps it could end with the letter mentioning that "In 2013 I sold the business, and am now {adjective/adverb} retired. Two25acres' exemplary work for me played a substantial role in making this happen.

Thank you, we discussed my writing it, printing it and his signing it. We wouldn't do it electronically. No threats, sorry if it came across that way.

For the past 35 years with two insurance agents, (the first agent retired) I do not believe I've spoken to either agent more than once or twice. Everything I've needed done, is done by the assistants who run the office. Those experienced assistants have been jewels and so helpful the few times I actually needed the insurance I had purchased.

With 15 years experience you too are a jewel.

Quotes (with reference) to your former boss and quotes (with names removed) from your clients would be good.

The assistant from the first agent was promoted to a roving supervisor who helped all over the area when assistance was called for, otherwise I would have followed her to any office she went to. Your clueless present boss to his distress (karma is a b) might find that his clients will leave and go with you.

Best of luck and I hope you find just what you are looking for, and treat yourself to chocolates and schadenfreude as your present boss struggles without you when you find it :)

A commendatory letter of recommendation should have all the things that are important to bosses that are not put into resumes, and which can't be asked or answered by HR execs. It should include the length of time working together, the reason for parting (i.e., boss's retirement), your good work related attributes (only a few, which could include: conscientious, punctual, detail oriented, friendly, good with customers, self starter, independent worker, efficient), the scope of your responsibilities (including the expansion of your duties over time), and your strengths and weaknesses. The weaknesses are hard to do because you don't want to unrecommend yourself. An example of how to do it is: Ms. X has a tendency to be shy, but when given opportunities for leadership, teaching and managing customers, she is vocal and effective.

This should be all on one page and no more than three medium paragraphs. Long essays won't be read, and men, as well as bosses, tend to be brief.