I took one to a physics exam in college circa 1989, when intelligence had emerged that another class would come and spray us with buckets of water and there was no way I'd expose my previous HP-15C to that kind of risk. The professor looked at me funny but I went through without any issues.

I'd purchased it at the Ito-Ya stationery store in Ginza where they still sold Hemmi slide rules well into 1985 and I still have it, as well as my dad's and a couple of Concise circular slide rules from the MIT Museum.