That's a nice little Terrier acquisition.
Based on my database, your #73749 was most likely shipped in the 2nd quarter of 1954.
It's an Improved I frame, 2nd version with ramp front sight and barrel rib, and a 5 screw frame. Therefore it's too early to be a Pre Model 32. The 'Pre Model' I frames are the Models of 1953 and only had 4 screws and then 3 screws after 1956.
Although yours shipped after the introduction of the Model of 1953, it does not have the engineering changes of the Models of 1953 which are the same as Model 32s, and that's why it can't be a 'Pre Model'.
Enjoy shooting that one!