Schlage IC cylinders, open top vs closed top

[tjohn]

I know this is a slightly old thread, but I would like to chime in to say:

1-Those are standard cylinders. not removable core

2- The difference is simply age. The closed top is how they used to make the cylinder back in 'ye olden days. They switched to the open cap with strip, I want to say sometime in the 70's. I would assume the holes in the bottom were simply how they drilled the bible holes. Those holes have nothing to do with keying/ejecting/etc

D Series Schlage still came with the closed top for a little while longer after all the other series were switched to the open top, but some were a little different in that it had a seam down the middle (two tabs sorta folded over)

[raven252000]

i just got a Tell dead bolt that uses the sealed top it uses a schlage "c" key way.when i took it apart it had 5 pin sets and 6 holes. but its a new commercial grade dead bolt with the sealed top.

[vitti]

again I'm still guessing here... If the holes aren't as beyond described then could be they be for aligning the cores for some sort of tooling either at the factory or for re-key/service? Or is that exactly what beyond was referring to?