Sorry if I disturb with such a dull question, RTFM, I know, but I was quite surprised that I was not able to enter 2E-3 on an HP-19BII (emulated). In any case the minus sign was set before the 2 so with all my effort I only got -2E3 what is not what I expected.
I should find a real HP-19B2 and some working batteries to test on a real thing, but may be someone here may shed some light on this matter before I get lost in the dark and dusty archives of my collection.
Ciao.....Mike