Wert, when a coin die develops a crack, it spreads under pressure when it hits the face of the coin. This is what you are seeing. Your comment about it looking like a weld is interesting because superficially it does look like that. The spot where the die crack is displayed on your coin is a primary area where I'd expect one to develop, from a denticle to a design element (bust in this case).
This era of coins features many variations and many were catalogued by a man named Hans Zoell and you can buy a Charlton-Zoell variety catalogue.
Considering your interest in finding and examining these types of coins, I recommend that you get one.
Wert: I had the same issue a short time back... and this was a response from a community member: Quote from pgrinh: Your bottom picture is Zoell variety number L72d. There are three total listed 1948 one cent Zoell varieties Bust to rim, none of which match your top picture..... This is a particularly prone area to Die Cracks for all denominations of the George VI coins. Hope this helps.
I see that Dvereckis ....Yours looks like what I thought a crack should look like...Mine looks more like some one welded the penny together (if you know what I mean). Nice coin you have there....I will have to keep my eyes open for cracks in coins from the mid 40's to mid 50's.