The PowerBook G3 Lombard can be upgraded to 512MB by using two 256MB modules (512MB Kit).

Standard Memory
64MB or 128MB Removable
Maximum Memory
512MB
Memory Expansion (No. of sockets)
2 Expansion Sockets
Memory Expansion
Install 1 at a time
Memory Sizes
64MB | 128MB | 256MB 512MB Kit
Memory Speed (Type)
PC66