That is a remarkable find in an uncleaned lot. Certainly some corrosion (sadly) but a rare variety. In my over 20 years collecting late Roman issues I've only found two examples of the Crispus closed gate type and neither matches yours. That is what makes ancient coin collecting fun ... you just never know what you'll find.
Thank you for the comments - and I agree completely. I really like seeking out poorly-described lots of ancients and then rooting through them to sort everything out. I learn a lot that way. And, if nothing else, it keeps me out of the taverns (to some extent).