Belgium revolver .38S+W/.44 Cal.

I have this revolver (6 rounds) that chambers .38 S+W bullet but the end of the barrel is about .44 cal. In other words the back end of barrel is .38 cal and the front end is about .44 cal. The weapon looks almost unused and has a safety lever on left side. Was this a design flaw or on purpose? Its the type made in the first part of 20th centry