At the beginning of 1958 Schwinn somewhat followed a new idea that started in 1957 having the year and then a letter at the beginning of the serial. That was weird and can't say what the heck they thought they were doing in 57. It looks like that mess was straightened out starting on 4/17/58 as the list shows but that's not what happened out on the floor for your serial number. Looks like your serial number has the year number and month letter flipped like previous serials of 1957 and early 58. The serial list is not perfect, and I've noted many errors were something went wrong when copying the list along with many other irregularities. The serial number date has nothing to do with any build date of a bike and when the bikes were built is anyone's guess. The normal time span from serial stamping to final build was approximately 2 months and that varied. The serial # was stamped on the bikes component, either the BB shell, drop out or head tube and then that component was later used to build a frame. I'd have to believe your serial number was stamped on April 23, 1958 and the bike was built sometime after that. And FYI, the 58 Hornets once again were equipped with a built in kickstand after Schwinn went cheap on this model in the mid 50's with a bolt on and rolled stem.
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New Number System Begins:
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04/17 ------------------ D836694 ------------------ D838593
04/21 ------------------ D838594 ------------------ D839915
04/22 ------------------ D839916 ------------------ D841530
04/23 ------------------ D841531 ------------------ D843350 =========> or 8D42291
04/24 ------------------ D843351 ------------------ D844959
04/25 ------------------ D844960 ------------------ D846571
04/28 ------------------ D846572 ------------------ D848468
04/29 ------------------ D848469 ------------------ D849860
04/30 ------------------ D849861 ------------------ D852272