The Cal-look Lounge

I've been trying to find definitive answers to this question, but there doesn't seem to be info regarding this anomaly/feature.
I've noticed on my '67 (and at least two other 67s) that the rear apron has a definite and noticeable outward bulge, as if to accommodate a larger muffler or maybe even a more angled heat shield on the inside of the valance.

Is this bulge unique to 67 bugs? or does it appear in earlier/later cars too?

1500

??? ... not sure I understand your response. Are you saying that this rear apron shape was specifically for 1500 model cars?
(my '67 is a 1300 Euro spec version)

Only 1500cc should have it like that
67 the only year that it is so
If it is a 1500cc, the engine cover is also different
But if you are outside Europe, it can be different
On export cars on certain details

according to Volkswagen parts catalogue the apron is the same for all 67 beetles sold in Europe and North America. On my 67 it also looks a bit like in the picture, it was originally equipped with a 1200 engine...

I'm afraid i don't think your information is correct  :-\
ALL 67s have the "flat bottom" engine cover (decklid)....there wasn't a different engine cover for different engine sizes. (Except for the convertible 67 which has the same shape, but with vents)
Based on the other replies, it seems that the apron bulge is present in 67s of all engine capacities.