Here are some interesting findings from the Places of Worship stamp issue:
1. The brochure states that Perak Tong (a cave temple) is in Gunung Rapat (south of Ipoh town centre).
In reality, Perak Tong is in Kampung Tawas, north of Ipoh town centre. Possibly, there is a confusion with Sam Poh Tong (another cave temple) which is in Gunung Rapat.
2. There is also a constant ring flaw on all the Perak Tong sheets. Rather than trying to describe the location, here is the picture. Do not get too excited yet since this is a constant flaw. Rare will be a sheet without the flaw.
Go check your own collection :-).