It's a plant sprayer.
I was sure baffled last week! Not much better this week, but it looks like an oil can nozzle.
A brass plant sprayer? Sorry for not having a guess for ages but I struggled with a few then we were away on holiday and then we had computer problems!!
Thank you for visiting. Hope you enjoyed the pictures. Any comment, or correction to any information or identification I get wrong, is most welcome. John