I was maybe 10 years old at the time (I'm 66 now). The apartment we lived in was my parents and i had no brothers or sisters, it was what were known as the "railroad rooms". Basically, one long stretch with the various rooms along the way. One end was the living room, the opposite end the kitchen and bathroom.The bathroom was quite large and fairly square. In addition to the toilet and bath/shower, there was enough room for a clothes washer (my mom used a clothesline, so no dryer) plus a small room to keep the ironing board and in fact to do the ironing in.
They were only one window, which was directly opposite the toilet and it had a fire escape outside it. The window had Venetian blinds, which were always completely down/closed and the window was kept locked. So, I was sitting on the toilet doing what I had to do when, for no reason. I can remember, I looked at the window. One of the slats was raised on the left side (from my point of view) and a large, single eye was staring at me.
I froze, then screamed terrified by this. I kept screaming until my father broke thru the locked bathroom door. AT THAT INSTANT, the slat in the blind dropped. I clearly remember hearing the metallic "ting" sound it made when it did that.
I told my father what I'd seen. He went straight to the window and raised the blind - nothing to see. Checked the window - it was securely locked. He then began pointed it out while trying to calm me down, how could someone have lifted one of the slats of the blind with the window down, closed and locked? I didn't know and i still don't know. But I am sure - absolutely positive - that I saw what I've just described. I've only shared this one other time - at least a year ago, I think, on a site called Pararational. One or two people responded with, "Gee, that must have been scary" type of comments, but it seems that no one else has ever had a similar experience.