Adler Timing Belt
The singer belts were not the correct size, sent them back. More measuring and education about timing belts and I determined that it requires a 448mm x 10mm trapezoid belt with 8mm between the middle of the cleats. There should be 56 teeth.
The only belt in this size is a rounded cleat instead of a trapezoid (flat). Ordered it from China, maybe it will arrive someday...