Conventional thinking suggests that those two bikes either got a replacement guard from a Jag, or one might have been repainted, and a top tube decal added. All the catalogs I've seen show the 57 and later Jags with tanks. An original paint frame should at least show some wear marks if it had a tank. Also, from the price lists, there was a base model with coadter brake offered for both the Jag and Vette most years. And a coaster bike may have the frame with the caliper mounts on the frame and fork. I've also seen og paint men's bikes with the ladies' chain guard, which has a brake cable keeper on it. So, it's a mix of what "should" be, and what actually happened at the factory!!!