This is the saddle tank of an 009 gauge Porter, which consist of the following 4 parts:
It only fits the new chassis of the Minitrains 'Krauss Steam Locomotive', which is also being sold separately at www.minitrains.eu.
The tank has been hollowed-out to be able to add more weight to the model with a product like 'Liquid Lead' or 'Ligquid Gravity'.
The tank also contains pre-modelled holes for short handrailknobs (Alan Gibson) and the tubing from the dome (0.45 mm nickel or brass wire)