Yeah, my reply is probably too late do do you any good.
No, the 160 was not made by Astro, although Astro has some interchangeable parts. Or, I could be wrong, and Astro made them for SP Air...and Mac...and Matco...and thirteen other custom-branded customers.
The AW135 specifically seems to be an Astro-sourced item, but the Mac AW140 and AW160 were apparently made by SP Air, the in-house number was 5135. The Matco MT1725 was similar. If you check that web site for SP5135, you'll see what I mean. Mac and SP Air go back a long way.
I just repaired an AW160 using some SP hard parts, obtained from
https://www.powertoolrepairohio.com/pages.php?pageid=14&breakid=1353
The parts list contains Mac, SP Air, and Astro part numbers. Who knew that air tools used "common" parts among brands? Well, Astro does, as they advertise parts for various other brands of air tools.