Described as a Soviet spirometer, model BCB-1 NOS.  It is only able to measured vital capacity and was used for military enlistment testing.  Probably from the 1980’s and it is likely a Metatest spirometer.  The dual scale is in liters and there are two separate (probably 4 liter) bellows inside.  When one bellows is used the 4 liter scale is active.  When both bellows are used the 8 liter scale is active.  From an Ebay listing.