page29

SIC page 4

The odd evolution of the 1530

At left, we have two apparently similar rules, both labelled as SIC 1530's. To the trained eye, the top rule is probably older, due to its shiny end braces, versus the matte finish ones on the lower rule. Additionally, the font style is an older one, and the SIC symbol itself is older. If this was the only picture you saw, you'd think these were just variants of the same type. How could they be anything else, having the same model number? Read on, but remember the title said "odd" at the top of the page.........

Here we see the left ends of the same sides of the rules as the scan above. The presence of the rounded end cursor is quite uncommon on rules with the shiny end braces. We also see to good effect the differences in font styles between the two rules concerning the scale labels. But there is another subtle oddity. On the top rule, the scale labels on the cursor lens are moved to the right, nearer the hairline, so that "e" log-log scale legends can be added. The later rule below, like all SIC rules I'm familiar with, lacks these. Hmmm. Interesting, but not huge. Let's turn the rules over and see what differences we find on the other side.

   Yikes. Not the same at all! Not even close! What's the deal here!?

     Let's start this time with the bottom rule, the known quantity. This is indeed a "standard" SIC 1530, with a serial number and all the other normal features. This rule is basically a modified 153, which is where I presumed that SIC got the model number from, since they just add a "0" on the end of existing RELAY model numbers. The later 1530-A is actually a modified RELAY 154. This info can be seen elsewhere on the site too, btw.
    The top rule, the older one, is obviously a modified RELAY 150! Same scale sets, just with the typical SIC mods added. That's it. But why?
    Did SIC plan to use the 150 layout first, then switched to the 153 type to get the trig scales on the slide, the preferred arrangement in the US? Is it a goof? Why the 1530 model number, shouldn't this be a 1500? I don't know. This is the only one I've seen like this. In fact, in the auction if I hadn't seen the back side of the rule, I'd never have suspected it to be like this. For now, another mystery, and another variant to watch out for!