GJ.11a, 1884 1c. Little Envelope perf 12, INVERTED OVERPRINT variety, mint original gum, very fine quality, rare, signed by Victor Kneitschel on back! (Image)

GJ.14c, INVERTED OVERPRINT variety, mint original gum, VF quality, rare! (Image)

GJ.22a, DOUBLE OVERPRINT variety, mint without gum, VF quality, rare! (Image)

GJ.29a, 1884 90c. Saavedra with INVERTED OVERPRINT var., mint original gum, very rare, with several signatures on back including Victor Kneitschel! (Image)

GJ.97a, with DOUBLE OVERPRINT variety, signed by Victor Kneitschel on back, VF quality, rare! (Image)

GJ.159, with W.Bond watermark, MNH, superb, very rare! (Image)

GJ.175b, with INVERTED OVERPRINT variety, very fine quality! (Image)

GJ.213a, 5c. Moreno, typographed, INVERTED M.G. overprint, MNH, excellent quality! (Image)

GJ.216a, inverted watermark, mint with tiny hinge mark, excellent quality, rare, signed by Victor Kneitschel! (Image)

GJ.250a, block of 4 with variety: DOUBLE OVERPRINT, one inverted. A very rare block, one stamp stained (the rest of VF quality), signed by Kneitschel (Image)

GJ.252a, fantastic block of 12 with DOUBLE OVERPRINT, MNH, superb, signed by Victor Kneitschel on back. (Image)

GJ.258, 1925 12c. San Martín printed on ribbed paper, M.H. overprint, mint with tiny hinge mark, excellent quality! (Image)

GJ.315, 12c. San Martín with period, perf 13½, M.I. overprint, MNH, extremely rare, signed by Victor Kneitschel on back! (Image)

GJ.415b, 20c. San Martín without period, DOUBLE OVERPRINT, used, VF quality, very rare! (Image)

GJ.493a, DOUBLE OVERPRINT variety, used, very fine quality, rare! (Image)

GJ.515a, Moreno 5c. typographed, with INVERTED M.M. ovpt, VF quality, rare! (Image)

GJ.518a, DOUBLE OVERPRINT variety, only known used, excellent quality, very rare! (Image)

GJ.527, 1918 20c. San Martín unwatermarked, M.O.P. overprint, mint, with a small thin in the hinge area, very good front, very rare! (Image)

GJ.532, 1920 12c. San Martín with multiple suns wmk, M.O.P. overprint, mint lightly hinged, VF quality, very rare! (Image)

GJ.570, 1935/7 5c. Moreno typographed with INVERTED M.O.P. overprint, one of the 4 known examples, excellent quality, extremely rare! (Image)

GJ.591, 1922 12c. San Martín with round sun wmk, mint lightly hinged, VF quality, rare!! (Image)

GJ.640b, 25c. Plowman, with INVERTED OVERPRINT variety, MNH (+50%), rare! (Image)

GJ.648a, 1P. Map without borders, printed on imported unsurfaced paper, with variety: INVERTED OVERPRINT, VF and rare! (Image)

GJ.664a, 50c. Petroleum, unwatermarked, with INVERTED WATERMARK variety, MNH (+50%), excellent quality! (Image)

GJ.709, 50P. San Martín (large size) perforation 13½, with vertical overprint type IV, fantastic used block of 10 stamps, VF quality (one with defect), very rare! (Image)