The very hot latest SDU sets are actually the re-release sets in new boxes. I also own a set myself for parts. The gas mask is my most wanted piece but it turn out not great. Cheap casting with rough surface and have sink mark on it, disappoint. The SDU vest is nice though.
Why is that? I notice that some of the original gas mask go for 30.00 + on ebay. There are only a handful of characters I could think of that use it.