A warm welcome to the ODK Forums, Leo.
The second pair of blades are actually 'lifters', to pick up the clippings and blow them into a catcher.
Mulching mowers weren't even on the horizon, when that machine was built!
Those plastic cowl/tank Mayfairs were 1970's models, up to about 1980 in their 'store brand' guise. And the same catcher was used on all the low arch chassis models, from yours until 1980; the Model 15 as listed
HERE.
By the way, we do have a specific forum for 'Identification of Particular Machines', so don't be surprised if this topic gets moved to it.
