After I was lucky enough to add an early 71 cookset to my collection I decided to look for some 71 stoves in tins. I picked up two on ebay for low prices (low for ebay) and they turned out to be consecutive years AS (53) and AT(54). This it appears was probably a transition year in stove and tin design. The stove gaining an SRV fuel cap instead of a solid fuel cap and soldered pin. The case changing from 10 hole design to 11 slot design. I already have the later Primus 71 tin and an Optimus 80 so I was pleasantly surprised by the thicker metal on the earlier cases. It's just a shame the cutaway in the pot support compromises the strength in this crucial area. Presumably why the later tin had a solid pot support.