Is this a factory tach?

[Nanook]

Just purchased this tach and it is for a 6 cylinder (It does work).

But the face plate looks a little different from the pictures I have seen posted. The plate has 2 notches for the mounting screws and has some extra letters on the bottom. All the others that I have seen do not have these features.
Can anybody shed some light on this? It apparently is from a 64-66 Chevy C-10.

[ray_mcavoy]

I have seen extra numbers printed on the lower face plate of many tachs (both factory and reproduction) ... they're hidden by the front tin once installed.

I haven't seen a fact plate with notches on the side like that one though. And the others I've seen all have a 90 degree stamped/rolled outer edge on the face plate (where the little orange pointers snap onto). Whereas yours appears to be flat.

I can't quite see the style of the face plate attachment screws in your pics, but I have noticed that the factory tachs used flat head screws while the reproductions are phillips.

The electrical hookup & "ground" marking on the back of yours don't look quite like the ones I'm familiar with either. The terminal that's marked "ground" on yours is usually the connection to the negative side of the coil. And the ground is via the mounting stud below it.

If you temporarily remove the metal mounting plate, it will likely reveal a decal on the back of the tach. All of the OE ones I have seen are marked with the manufacturer (SUN electric corp.) along with the model number, number of cylinders, and terminal identification.

[Nanook]

Here is a picture of the back.....

[ray_mcavoy]

Interesting ... the back of that tach looks significantly different than the ones I've seen. But all the ones I've dealt with have been V8 tachs that were made for GM by SUN. I wonder if GM might have had a different manufacturer make the 6-cyl tachs for them?

[Nanook]

I should add that I bought this on a recent trip to Canada...so it may have come from a Canadian made truck.