I work for a bank and I'm applying for a tourist Schengen visa via the Austrian embassy. I have gotten a NOC from my employer, which has the bank logo on top and states since when am I employed there, my designation and that my leave has been approved for the dates I intend to travel. It's also signed by HR. However, they're saying they don't have any stamp to use on that letter. I was wondering if this could be an issue or will the letter I have be alright?
I made a Schengen Visa application in March 2018 and got it successfully. My employer only issued a NoC on their letterhead with logo, name and contact details and my HR signed it for me just like your case.
Thus I can confirm that if your letter is signed with the company's logo and details on it, it should be fine.
You can refer to this page for more info.