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I looked up the aircraft and found that production stopped in 1945. Those engines are modern turboprops, apparently P&W PTBA-45. The original http://en.wikipedia.org/wiki/Dornier_Do_24 seems to be engined with radials.
My questions are: Would this be a lot of work? Why would they do this? And finally (tongue in cheek): Isn't this "defacing" a historic aircraft?
Photo © Javier Gonzalez - Iberian Spotters
Photo © Andreas Barowski