Search for all terms: Material: carborundum. 3 records found.Records with Images1. Forward Spark 'B' Wavemeter No. 2006, by War Department, Britain,... 2. Forward Spark 'B' Wavemeter No. 1511, by War Department, Britain,... 3. Forward 'B' Spark Wavemeter No. 1339, by War Department, Britain,...