Cosmac VIP, ETI-660, Dream 6800, and Chip48 interpreters all have different font data. This can effect program behavior because of pixel based collision. Some programs have text that looks off center as well.
Tested in Cosmac VIP and ETI-660 in Emma 02, Dream 6800 in MESS/MAME, and Chip48 in Emu48 for hp48sx.
Used cosmac VIP chip8 ram sha1 8AA634C239004FF041C9ADBF9144BD315AB5FC77
Used eti rom sha1 C0C4951E02F873F15560BDC3F35CDF3F99653922
Used Dream 6800 with original CHIPOS ROM. sha1 60F26E57A058262B30BEFCECEAB4363A5D65D877
Used chip48 2.25
https://groups.google.com/forum/#!searchin/comp.sys.handhelds/2.25/comp.sys.handhelds/z8KoBcbCExQ/q4VsdUu-1ssJ
which is sha1 16AB1BAC7D4861C26EFA4DF29E3AA3CE1BD8F7E5 after removing transfer dependent 13 byte hp header.
Images showing the fonts, and text with their binary representations are attached.
I suspect there are variants of the chip8 data used by the cosmac and telmac 1800. The author of chip48 had a telmac, but the font used by chip48 does not look exactly like the font seen in the chip8 ram used by Emma 02. (same chip8 ram data is used for cosmac and telmac)
https://groups.google.com/d/msg/comp.sys.hp48/eKdWisxs-_Q/63e9bVZcOkgJ
I intend to do more research into this.
chip48font.txt
cosmacvipfont.txt
dream6800font.txt
eti660font.txt