Its a japanese industry standard for quality, similar to TUV in Germany and DOT in UK etc......
A simple google turned up this.....:
"Safety Standards:
JWL-Japan Light Alloy Wheel (JWL) Standard for Passenger Cars. The Ministry of Land, Infrastructure, and Transport requires that aluminum wheels for passenger cars bearing certain plated numbers sold in Japan bear the JWL mark. The JWL mark can be displayed on wheels that have passed the standard through a self-certification system.
JWL-T-Similarly, the ministry requires aluminum wheels for trucks and buses (with 1 and 4-number plates) to bear the JWL-T mark. Even if a vehicle is classified as a passenger car bearing certain plate numbers and is equipped with LT tires as standard equipment due to its GVW (gross vehicle weight), it must use aluminum wheels bearing the JWL-T mark.
VIA-A third-party entity called the Vehicle Inspection Association verifies whether a product meets the requirements prescribed by the JWL or JWL-T standard. This association permits a product to bear a VIA mark if it passes rigorous quality and strength verification tests conducted in accordance with the JWL or JWL-T standard."
I knew you would know