Hello Paul,
Sorry for not replying earlier! The batman reference got coined here [a bit tongue-in-cheek, I suppose
] for the intricately carved version of the hilt (resembling the comic character) as well as the rare scabbard type (resembling the comic bat emblem). I'd suggest to restrict the discussion to keris with this special scabbard crosspiece though since the general hilt type seems to have been in widespread use throughout southern Sumatra.
This scabbard type seems to come in several variants which may point to either several locally restricted and probably neighbouring traditions or a generic pattern that got less strictly enforced, presumably because there was no uniting power (keraton) or the region being too far away from any center of power (like Palembang).
Here are some more pics and I hope others will chime in with examples, too!
Regards,
Kai