(The Charger was purchased from a Honda Dealer for a VFR 800 VTEC which had a wet maintenance-free sealed type Battery).
http://ppdocs.motorcycleproductindex.com/pp126996d1.pdf
In the first photo, the label says "Automatic Charger for 12V Lead-Acid Batteries" & on the box in the second photo, next to 12V, it has 3 Battery symbols, Normal, MF & GEL.
This confirms to me, (as did speaking to Optimate), that the battery Charger is suitable for all 3 types of Lead-Acid Batteries.
The Optimate 4 is recommended for AGM/MF, Standard, GEL and spiral cell batteries, as above including AGM.

http://www.optimate.co.uk/OptiMate%204% ... eaflet.pdf