This is an N scale replacement sand box for an Alco C-855B Kit that was purchased before the 1st of August 2016.
It replaces the front left sand box which did not fit on the earlier locomotive shell. This part is not required with any C-855B kit purchased after this date.
This parts is designed to be printed the FUD & FXD materials and they will require cleaning before painting. I recommend washing with warm soapy water then soaking in 'Goo Gone' or similar product for about 24 hours. Then rinsing off with warm water and allowing to dry.
For more information please see my blog - www.jamestrainparts.wordpress.com