RSA 1981 20c State Theatre with RIGHT MARGIN IMPERFORATE. SACC 494a. Superb MNH. See research below.

As per scans below.

Ignore the current SACC (2019-20) value for this item.

Why? 

Well when this item last came to market - in 2000 as lot 539 in the then Stephan Welz/Sotheby's auction - the listed item was catalogued at R 3,000 and the Imperf M/Sheet of the same issue at R4,500. 

At the same time two other RSA varieties - the Transkei Legislative Assembly SACC 244a green omitted and the 50th Anniversary of Broadcasting 356a missing black were catalogued at R13,000 and R7,500 respectively.

So, the listed item was catalogued at:

67% of the same set imperf m/sheet, 23% of the missing green SACC 244a, and 40% of the missing black SACC 356a.

But now in 2020 the listed item is catalogued at R12,000 whereas the imperf m/sheet is R150,000, the missing green SACC 244a is R240,000 and the missing black SACC 356a is R280,000!

There were apparently only 5 of the listed item SACC 494a, more than 10 of the missing green SACC 244a, and 10 of the missing black 356a. There is not other history of SACC 494a than the 2000 sale.

The current SACC value of 494a seems nonsensical. The relevant sections of the 2000 SACC are included for reference below.