The company started in 1997 using leftover military bikes and started making their own after all the surplus bikes sold out.
The ones they made were very similar to the original surplus bikes., the swedish m42 bike: " m/42 - The most well-known Swedish military bicycle. It was produced by several large Swedish bicycle manufacturers (Rex, Husqvarna, Monark, Nymans) from the 1940s to the 1950s with a maximum of interchangeable parts. It uses a rear, one-speed Novo C coaster brake hub, and a Husqvarna-produced front drum brake (chain-operated by an integrated right-hand lever). In addition, it has a large, sturdy rack with a tool box and storage tube for a short frame pump. Weight: up to 26 kg (57 lb.)"
"The current Kronan Bicycle has been modernized slightly, but has the same basic design as the original. It is assembled in Poland using parts from Asia. The original Kronan factory was in Malmö."
Since they resold their first bikes, and later ones were built by different manufacturers, now made in Poland, there may not be a date code on the serial number. It would need at least 5 numbers or more if they kept track of year and sequence. HK803 might be a registration number, judging by this pic: