Sorry, the $13.63 was for an MC-28, which is the matching base for a 526 (among others); I have 2: one bought new in 1983 (from Mize Supply, also in Virginia) with a bunch of other boxes at a ridiculously low price (sale plus super % off because they gave me the same deal as the mechanics at the new Hershey plant – I was Process/Mechanical Engineer) and a second that I bought used 2 years ago with a 526.
Photos and details in this post on HSM.
However, assuming the 526 was bought at a similar price as the MC-28, it was still a good price, here's what a new MC-28 lists for:
View attachment 492230
and a new 526:
View attachment 492231