Here I am...
The image is of the Sm-88 (thanks Paul..), which was a 1939 export projects for a two-seat light bomber-reconnaissance aircraft. It was twin-engined (two DB-601 basically, even though other engine has been considered). Actually the version displayed was the second one, the first (from this on, I am relating new results from my research, will find them in my next book ) was a single boom, twin-tail, two-seat, one powered by two Gnome-Rhone or Walter Sagittas. Marchetti saw the Fokker G-1 at the 1938 Paris Salon and decided for a twin-boom design. BTW, the first SM-88 was originally called SM-86W (W for Walter...), and yes, it was an evolution of the SM-86 dive bomber....
Actually, the Sm-91 was only related to the Sm-88. The wing was different, although made of laminated wood in both cases, but was shorter (the project had a very high wing-load, in excess of 260 Kg/m2...). Naturally, Paul is right, Hesham: the original SM-91, submitted at the second round of the 1938-39 Caccia Combattimento (alongside with the famous IMAM Ro-67 and others) was a three engine with Db-601s (two tractor and one pusher), other engines considered, as the FIAT A-38, and was a heavy fighter with a secondary duty as fast light bomber (bombs under the wings). The Sm-91 was ordered as two prototypes, but the SM-88 too was ordered... one machine. Later, the SM-91 was first developed in a two-DB601 version (for lessening cost), then cancelled altogether (circa July 1941). The Sm-88 continued and divided in two versions (SM-88B for bomber, and SM-88D for Distruttore, zerstorer, self-explaining) and went on to DB-605 and an all metal construction (actually is more complicated, but I want to sell my book.. ;D ). Then, late 1942 the Sm-88B was cancelled (standard light bomber was to be the Cant-1018 Leone and Breda evolution, the BZ-301) and the SM-88D changed to SM-91, a two-DB-605 heavy fighter (seven 20-mm Mausers...) to attack dense bomber formation at day. The first SM-91 (new style) was so actually the SM-88 prototype. It flew first in March 1943 with the original long central nacelle. After a mishap, it was grounded and resumed flying in July 1943 with a shorter nacelle. This machine was weapon-less (and a "lot of other things" - less). A second prototype was started in early 1943 but completed only in early 1944. This was to be a day/night fighter (some tests were conducted in the night configuration even on the first prototype). It flew in spring-summer 1944 but was gravely damaged by an Allied incursion (strafing) on the Vergiate airport in December 1944. It was disposed of after the end of the war.
One more note, from July 1941 to October 1942 the SM-91 designation wasn't in use officially but SIAI Marchetti used it internally to designate... the various projects that led to the SM-93, but this is another story.
Satisfied ? 8) ;D