On 26/03/20 5:58 PM, stes wrote:
> 
> Hi,
> 
> Is there an easy way to see in the squeak image file name what the "image
> format" number is ?

Yes. Use ckformat command. See http://wiki.squeak.org/squeak/6582

$ ckformat foo.image
6521

> Is the old "unix" squeakvm able to run 5.x images at all or should one use
> the "opensmalltalk" VMs for that ?

You will need opensmalltalk VM for 6521. See 
http://wiki.squeak.org/squeak/6290

HTH .. Subbu