PrimaLuna Prologue Classic Question!

Is the transformer compartment (?? behind the tubes) of this integrated amp supposed to be hermetically sealed or give the appearance of being so by a plastic type shrink wrap??!  I’ve had this wonderful little amp for several weeks now...been playing it for multiple hours nearly every day without so much as a hiccup and then, just this evening while dusting around it, noticed the sheen of some sort of clear membrane covering the entire rear metal enclosure including ventilation slots.  The unit was demo’ed and sold to me in this state.  There is no mention of anything akin to this in the owner’s manual.  Maybe it’s supposed to be that way???  Of course these discoveries are always made when everyone is closed for the evening.  Does anyone know if this is a common thing with these amps...is this anything to worry about?  Thanks.