I think it's a great result, especially considering your age. In fact, your level at diagnosis of 6.1% gives food for thought.
I mention age, because the rate at which we "Glycate", (turn our blood sugar into Glycosylated haemoglobin, giving us our HbA1c numbers) increases with age. As a result, our HbA1c increases with age anyway, even for a non-diabetic.
One investigaation of a group of non-diabetics showed an average increase from just over 4.9% for under 40s to almost 5.6% for over 70s. So at 75, your age, you would be, on that scale, at a level of 5.8% anyway!
Here's the study
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551641/
This also means your average blood sugar levels (as taken on your meter) would be LOWER than the ones xyzzy suggests (sorry xyzzy!) because you are probably getting higher A1c, because of your age, from the same BGs as a younger person with lower A1c numbers.
Hmmm
I see you were 6.1% on diagnosis. That's just 0.3% above the average for this group.
Did you do an Oral Glucose Tolerance Test as well?
ANYWAY, all means your figures are fine. No excuse to slack off though, just keep to it!