So these are some NOS 30 year old midranges. I have been looking for a pair for the collection.
Hard to tell from the picture, but it is a treated cloth dustcap and the paper looks like it might be fiber impregnated. Later versions used a shiny black mylar dustcap.
Looks like there may be some sensitivity mismatch, but the sweeps were clean as a whistle so I suspect the ferrofluid is still ok. Realistic claims a more or less ruler flat response from 1K to 10K.
My thoughts on that are "we'll see".
Sooooo... I have a pair of the Realistic cone tweeters, these mids, and currently searching for a NOS pair of the paper cone 8" or 10" woofers to complete my all paper cone standmount design. If I find time to throw these on a baffle, I will take some FR measurements.
I have a signature.