Those shallow mudguards are from the 1930s. From the catalogs, Herc mostly used the "HERCULES" or a simple spoke style chainring similar to the Raleigh, but this style does appear on the juvenile models, so it's not far fetched to assume it could have been also used on full sized roadsters at times. 3 speed hubs were an option back then. Also, back then, these roadsters either came with the enclosed chainguard or no chainguard, so this later addition helps point to a pre war date. I'm thinking this is a pre war Herc.