Received a verbal offer Tuesday - 3/22 with the company recruiter stating an official letter would arrive Friday - 3/25 or Monday - 3/28. I followed up on Tuesday - 3/29 to see if they needed any additional information from me. They did respond saying they were working on internal things and would keep me updated on that same day, but haven't heard anything.

Previous offer letters have been either same day or within a day or two of the verbal offer. So I'm not sure if this is a common thing or if its my own self-doubt getting to me. If it matters, the company size is about 150-200 people.