GJ.3A, 1883 3c. GREEN, mint original gum, excellent quality, very rare, signed by Marcelo Loeb on back. (Image)

GJ.6, used, barely cancelled, excellent quality, signed by Kneitschel on back. (Image)

GJ.9, mint original gum, signed by Victor Kneitschel on back, VF quality, very rare! (Image)

GJ.10, mint, very fine quality! (Image)

GJ.11, mint with original gum and tiny hinge mark (it appears to be MNH), signed by Victor Kneitschel on back, VF quality, very rare! (Image)

GJ.14b, block of 4 with DOUBLE overprint, one faint, VF and rare! (Image)

GJ.19, mint block of 4, 2 stamps MNH (+50%), very fine quality! (Image)

GJ.19a, with INVERTED OVERPRINT variety, very fine quality! (Image)

GJ.32, with variety: Very dirty overprint due to excess ink, fantastic, VF quality! (Image)

GJ.35, complete sheet of 50 printed on VERY THIN PAPER in light gray (extremely rare!!) + other 2 sheets of 50 (without the sheet margins) printed on THICK paper in the 2 shades of gray very different between them, a few stamps with minor defects, most are excellent, spectacular group! (Image)

GJ.73, 1918 12c. San Martín in block of 4, all WITH W.Bond watermark, MNH, excellent quality, very rare! (Image)

GJ.88a, 1925 1c. San Martín w/o period, with INVERTED M.A. overprint, MNH (+50%), superb! (Image)

GJ.104, 10c. San Martín typographed with M.A. overprint, complete sheet of 100 stamps, MNH, superb! (Image)

GJ.138, 1915 1c. Plowman, without watermark, M.G. overprint, very rare mint block of 4, 3 are MNH (+50%), very few known! (Image)

GJ.141, block of 8 with DIAGONAL OVERPRINT (in the right stamps it is much lower!), also the top left stamp with RETOUCH on "9 DE J", VF quality! (Image)

GJ.245, 1923 1c. San Martín with period, perf 13½x12½ and M.H. overprint, excellent quality, very rare, signed by Victor Kneitschel on back (Image)

GJ.299, 1918 5c. San Martín with SERRA BOND watermark and perf 13½x12½, MNH (+50%), in pair, one example without watermark, excellent quality, rare! (Image)

GJ.406a, with INVERTED OVERPRINT variety, MNH (+50%), excellent and rare! (Image)

GJ.425EN, vertical GUTTER pair, VF! (Image)

GJ.427EN, vertical GUTTER pair, VF! (Image)

GJ.492a, pair WITH AND WITHOUT period after the value, excellent quality! (Image)

GJ.497a, block of 4 with DOUBLE IMPRESSION variety of the M.M. overprint, one with tiny hinge mark and the rest MNH (+50%), signed by Victor Kneitschel, superb! (Image)

GJ.524, 1912 12c. Plowman perf 13½, fantastic block of 4 of excellent quality, the stamps below are MNH, rare! (Image)

GJ.525a + varieties: Block of 4 with 3 interesting varieties: "P with 2 periods", "P with comma", and "short P", excellent quality, very rare! (Image)

GJ.555, mint with tiny hinge mark, excellent quality, rare, signed by Victor Kneitschel on back (Image)