Signetics started as an IC manufacturer. In 1975 they were bought by Philips Semiconductors, which is now NXP. Interestingly the address in the datasheet, I think, was the original site. Today, it’s home to a Lowe’s Home Improvement Store. According to this Wikipedia article, it was created by...
I think there are a LOT more than. mistakes in datasheets are really very common - and sometimes never get corrected at all. Microchip for example do release updated datasheets, but they tend to add more typos to replace any they might have corrected
It's all but impossible to proofread something you actually wrote, simply because your mind knows what SHOULD be there, and corrects it for you without you noticing. I think the best solution is two different people, you both write (different) datasheets, then swap for proof reading.