The 244 was already in production in the late 1940s; it did not appear only in the 1950s. The standard reference on post-war production, “Collectible Stars” by Jens Rösler and Stefan Wallrafen, lists two variants of the model: an early one dated to 1948/49, and a second whose manufacture ran until 1954. A seller's statement that a 244 G was made in Hamburg between 1948 and 1949 is therefore perfectly plausible in principle.
The exact years are not given consistently across the literature, though, and since the pens carry no date themselves, dating an individual example comes down to placing it by its shape and fittings. Anyone who wants certainty will have to compare the pen with the illustrations and descriptions in the relevant collectors' literature. The suffix G denotes the trim variant, not the year of manufacture, and on its own says nothing about when the pen was made.