VARIATIONS
1914: 4-digits have thinner dies than 3-digits.
1917: Type 1 - Straight "7" of date 222 - 26706 (26,485 S)
Type 2 - Curved "7" of date 32270 - 33419 (1,150 S)
1918: Type 1 - Flat 66 - 39856 (39,791 S)
Type 2 - Embossed 42321 - 53903 (11,583 S)
1940: 4-digits have no hyphen.
1958-59: Type 1 - Fully reflective 1 - 1-000 (1,000 P)
Type 2 - Non-reflective 1-001 - 217-169
1976: Type 1 - Plain steel 1 - 356-441
Type 2 - Galvanized steel 381-583 - 382-644 (1,062 P)
1977-78 MONTH Stickers: "S A S K" (Serial printed over "A" and "S")
1979-91 MONTH Stickers: "S K" ("OCT 79" seen)
Month and year combined on one sticker "JAN 91" - present,
although "SEP 90" also seen.
Day sticker added 1996, "DEC 96".
