He will be able to tell in the darkroom or tent by unrolling the paper until he reaches the film. If it is attached with tape then it is unexposed, if it is free to flail about it is exposed. If he is going to measure it as suggested earlier he will ascertain any way whether it has been exposed or not. Personally with masking tape I'd guess it was exposed. The original would have had a paper tape round it.
Originally Posted by snederhiser