I thought I would bring the Model 5 thread to the top again. In the last 1 1/2 years I have bought/acquired two older Model 5's. Neither had sheaths.
I bought a sheath for the 5-7 a while ago, but only recently found a sheath for the 5-8. It isn't perfect, but considering it is around 60 years of age, it is not bad.
I have come to realize buying older sheaths, by themselves, price wise, can range between, "not bad" to "dear, we need to take a mortgage out on the house".
The 5-7, which I think is a late 40's to early 50's, based on the spacer arrangement. BUT I have been wrong before, many times!!