Partial overprint and overprint on the reverse are related and usually due to folding over of sheet edges during overprinting. Such errors are attractive and very rare.
1945 Mostar provisional issue, block of four of Ruđer Bošković stamps (Mi. 15) from overprint positions 89, 90, 99, 100 (lower right corner of the sheet). Partial overprint and overprint on reverse due to paper fold. Ex Tiberio. Certificate Vilfan, Marinšek.
