Joel S - I'd like to supplement the info provided by Jeff and Gerry, and assist with further information for ole Don T, on what exactly makes the "Model 169" an extremely desirable CC.
As was mentioned, production records identify 4005 units produced, all in 1974. It is the 2nd lowest production unit of the IH CC models (the model 800 Quiet Line being the lowest production but it was apparently discontinued due to low sales volume). The 1x8/9 series began production in 1972 (if I recall correctly, or maybe late 1971) having the 149 with 14hp as the top of the line unit. The 169 was added to the production line sometime approx. March 1974, and was apparently due to consumer demand for greater horsepower.
The 169 was the 1st IH CC unit to provide 16hp and was primarily equiped with a Kohler K341A 16hp engine with 13 cooling fins on the block. It also appears Kohler was making a casting change to their K341A sometime in 1974 as well since some of the 169's came equiped with a 12 cooling fin block. The 13 cooling fin block did show up in a few early 1650 Quiet Line units as a Model K341AQS but the 12 became the standard block and the 13 production by Kohler seems to have ended in late 74 or early 75.
The 13 cooling fin block actually appears to be more common in the 169 based on Forum member reports of which engine they have. There seems to be no known method to distinguish the 13 fin vs. 12 fin block from the Kohler model, serial number or spec numbers. You have to count the fins to determine which you may have. The 13 fin block is actually a thicker casting, and highly desirable by Pulling enthusiasts since the block can be bored to a full 4" which the 12 fin block cannot (I believe the max bore for a 12 fin is 3 and 7/8").
Also, the Kohler block spec'd to IH CC use is somewhat a rarity since the base is cast differently than the standard Kohler style tall base or even the "eared" base used for a JD unit. So a 13 fin Kohler with the correct IH CC base is going to be very difficult to locate, and may have only been produced by Kohler for use in an IHCC (although I have no actual data on that).
The 169 also appears to have been a hurried addition to the IH product line since later when IH introduced the Quiet Line series (late 1974) the model 1650 with 16hp was advertised in some IH literature as the most powerful Cub Cadet produced by IH (as if the 169 was forgotten).
The 169 was also the first CC to include a Maintenance Minder (more commonly called an Hour Meter and also noted as such in the parts book), which became standard on the Quiet Line series.
With further regard to "rarity" of the Kohler 13 fin block, as Don T points out he had a Bolens with a 13 fin. This is exactly why IH introduced the 169. Most competitors had a 16hp unit and IH had planned a 16hp for the 1650 in the Quiet Line series but hurried the 16hp engine into a model 169 to be competitive.
I must close by saying most of the information I've provided here is supported by some details obtain from IH archives but I don't have the exact references. Paul Bell is a more knowledgeable member on here and may provide any correction as appropriate to my details.
So, all in all, the Model 169 with an original 12 or 13 fin Kohler engine, and having a producion of only 4005 units, and being the only 16hp with a direct mount or hard mount to the tractor frame (the 1650 used rubber ISO-mounts), is quite hard to find in operable or restorable condition these days. I found mine in a junk yard many years ago. Here is a pic I posted before but it looked pretty much like this except it did have the engine in it when I bought it (I remember the day I saw it and couldn't believe it. I bought it for less than 3 figures, and the yardman told me I was lucky it hadn't been crushed). You can see another pic in my profile by clicking the my blue letter name.
Brian H - I'd also like to supplement Joseph S info on the Model 129 with a 44A deck. I've had several 129 units over my time and believe most were equiped with a 42 or 44A deck. I believe the 129 with a 12hp Kohler makes a very sweet tractor, and the 44A deck is pretty much a standard use or ideal size with this 12hp unit. The 12hp engine provides quite sufficient power to operate the 129 hydro speed control, and plenty of power to operate the 44A deck quite well. Many of the earlier 12hp CC units were equiped with a 48" deck and I believe 12hp was sufficient for those as well. If you're planning to mows hills or slopes you may find the tractor speed slows down but this is most likely more of a problem with the tractor hydro speed control (trunion on the pump) than the combined power need of the deck and tractor speed. This also depends on the incline angle but I would venture to say you won't mow with the tractor at full ground speed. This also assumes the 12hp engine is "up to snuff" with good operational performance. If it's tired it probably wouldn't handle any deck very well.