Volkswagen Australia introduced the first Superbug, the 'S', in February 1971. It had the MacPherson strut suspension, double joint rear axle and twin-port 1600cc engine like yours, but with a flat windscreen and a dashboard just like the earlier Beetles.
In April 1973 the Superbug S was replaced by an updated model called the Superbug 'L'. This model was mechanically the same as the earlier S, but had the big curvy windscreen, shorter front bonnet, 'elephants foot' rear tail lights and a completely new padded dashboard with a binnacle speedo and two-speed fan. It was updated in 1974 with 'negative steering roll radius' geometry on the front suspension, and in June 1975 with rack and pinion steering and front blinkers in the bumper. The last one was made in November 1975, so there is no such thing as a 1976 Superbug. Look at your chassis number - the third digit is the year ('5' for 1975 etc). Like all Australian-sold Beetles after 1968, yours was NOT made in Germany - it was made in Clayton, Melbourne, by 'Motor Producers Ltd', a company owned by VW Germany, using German-made 'CKD' kits with some Australian-made components. The Clayton factory was sold to Nissan in early 1976.
No they're not that rare; there are still plenty about but it's getting harder to find really nice ones in original unmodified condition. VW Australia's sales figures for the Superbug L were:
1973 - 6,620
1974 - 2,025
1975 - 1,930
The 1976 Beetle that replaced the Superbug (a 'bitsa' using the old 1300 body and pan with Superbug engine and gearbox) only sold 1,159. The Passat sold 4,113 in 1975 and 3,945 in 1976, and the Golf 4,429 in 1976 - the aircoolers were on the way out.
More Australian VW history here
http://www.clubvw.org.au/history/history.html
Your car is 36 years old and its value is purely dependent on its condition - immaculate, basically straight or ratty? I hope your Superbug goes to a good home and someone who will look after it.
