Zeiss 523/16, 1/500th Shutter Speed Issue

Just got a Zeiss 523/16. It has the Opton Tessar lens. Can't figure out why the shutter speed won't go to 1/500. Other speeds work great and my first roll of film looks real good. Feels like the adjustment wheel to set the speed hits a hard stop just past 1/250th. In other words, it does not feel sticky or gummy at all.
Any ideas? Is there some sort of lock-out that I don't know about? Also, anyone got a manual? I've checked the usual sources but this camera is not specifically listed.

If it is a compur shutter the speeds set easily but you need to push it hard to get to the 500, the first time I used a compur it felt as if it was against a brick wall, but everything is a lot harder for the 500, it is harder to get the setting ring to set against the speed, and the shutter cocking lever feels so stiff that it feels as if you are going to break the shutter, I never have yet and have several old cameras with the compur, a voightlander,Rolleicord, retina 1, contina folder, all with compur shutter and shutter cocking lever and all are the same, Hope this helps as the Zeiss Ikon MF folders are great cameras capable of taking great photos,
Richard

Is the shutter uncocked when you are trying to move it to 1/500? It won't go to 1/500 if it is cocked. It also requires more force since you are cocking against a heavy spring booster for just this speed.

I had one compur shutter where the booster spring (this is what makes it hard to get to 500 even when uncocked) was bent or something in such a way that I simply could not cock the shutter. I trimmed about a millimeter off the end where it is pressurized by the shutter speed ring movement, and now it cocks fine.

Thanks

It does have the Synchro-Compur shutter.
Just tried it and, exactly like you said, it went straight to 1/500 and is simply firmer than the other shutter speeds.
Thanks guys,
Tom C