Hi msnpr,
according to my understanding what you provided is a job offer, or they classify it like that.
What they want actually is a letter of reference being issued when you started working = in this case, your "acceptance" of the job offer.
PS the date on the letter should range between your last day when you fulfilled required work time experience and the day of application. For example, if fulfilled 2 years in March 2012 and you applied in April 2012 then it should be March 31st 2012. Something like that, you got the point.
If I am wrong, somebody please correct me.