In #132 @sgillies suggested an srid keyword argument to the wkb.dumps function.

Currently dumps has a include_srid keyword argument, which defaults to False. If set to True it does work as intended, although there is no way in Shapely to set the SRID of a geometry without poking the GEOS internals (GEOSSetSRID/GEOSGetSRID).

Are you still amenable to an srid=4326 style argument to dumps? If so, does it need to clone the geometry before exporting, otherwise the function will not be idempotent (although not in any way visible from Shapely).