Ok it looks like it is a .46, the bore is 0.845 inches and the stroke is 0.83 inches, which works out to be 0.465 cubic inches for displacement or 8cc. I might be a little off though on the measurements.
The outer cylinder diameter looks to be about 0.9865 inches or about 25.057 millimeters.

Pe, Does that look like your cylinder sleeves might fit OK or not?
Thanks