On the left, a grille of the model BL (small car): with a round hole to insert the crank.
On the right, a grille of the model BN (=B, big car): with an oval hole to insert the crank.
On the cylinder head you´ll see 11 (= Perfo, left on the photo), or 11 D (right on the photo):
The ´Malle Plate´ model (on the left, with visible spare wheel) was produced before June 1952.
The ´Malle Bombée´ model (on the right, with integrated spare wheel) was produced after June 1952.