In addition to the original D-LI90 battery for Pentax K-5 (and other recent cameras), B&H is now offering the D-LI90(E) for pre-order. The specs seem identical: 1860mAh, 7.2V. The only difference is that the new version costs $10 more. Is there something else?
The E suffix usually signifies compliance with European standards on Restriction of Hazardous Substances (RoHS). They simply have fewer elements which Europe does not like.