have just spent some minutes typing the comments below - so, whilst I appreciate you have both posted comments very recently, indulge me in letting me not waste my thoughts. thanks

""thanks julie - think the spout too narrow to accommodate a pen, and it really is a proper drinking/pouring spout shape. However, do take your point about the shape and slightly concave top being reminiscent of an inkwell - but the missing handle is a mystery. Would agree with you that feeders do have handles, normally - but I guess there are exceptions to all rules. The spout lip has now become, with the passing of time, damaged slightly - and you really would not want to put your lips on what might be a sharp edge. Looking carefully, it does appear that originally the spout edges were ground and slightly bevelled.
rosie - I'm warming to the idea of dicussing nipples

but seriously thanks for the inkwells link - really fascinating when you look at their history. Perhaps now that Ivo has finished writing about 'cuspidors' he might like to start a volume on inkwells.
When I saw the large ground/polished concave pontil mark, I assumed this might be perhaps even pre 1914 - but maybe not really quite so old. I'm also wondering if there might originally have been some kind of rubber stopper/valve inserted into the hole after filling with a liquid - thus preventing any spillage even if the object was dropped or laid down. All those with handles have large openings and thus need a handle to hold and steady them. If this example had a completely closed top then spillage would not be a problem, and a handle might be dispensed with"".