I too have an "oil painting" in my collection of Saving the Colours by De Neuville, It is dated from circa 1881 and looks like an original, except that it is an oleograph produced by a chromolithographic process which fell out favour at the end of the 19th Century. It was a type of screen printing on canvas and a popular way of reproducing well known pieces of artwork beginning in the early 1800s. It too is unsigned and on the back of the canvas there a printed is a coat of arms with the inscription 'National Fine Art Association'. It used to hang an officers mess in Dublin and was given to me a few years ago. The oleograph was in dire need of repair. I restored it and if anyone wishes to see before and after pictures please feel free to contact me.