Introduced: circa 1963 (discontinued circa 1968)
Back in the early 1960s when Arnold-Rapido was almost single-handedly creating N scale, one of their first releases was this EMD F unit model. Now, whether it's an F7 or an F9 is up for debate, as I've seen them called by both names. However, Arnold's own magazine ads called them F9's, so we will defer to them.
The first Arnold-Rapido advertisement that I am aware of appeared in the 7/62 issue of Model Railroader. It refers only to Arnold's Baldwin Switcher and makes no mention of the F9. The F9 first gets mentioned in an Arnold-Rapido ad in the 7/63 issue of Model Railroader (A/A dummy/powered sets painted for B&O and Santa Fe), once again in the 1/64 issue (erroneously referred to as an F7 in a Trade Topics blurb) and finally in a 2/64 MR article extolling the virtues of the new "OOO" scale trains (again, erroneously referred to as an F7). The 3/64 issue of MR contains the first AHC advertisement for Arnold's "Pee Wee 1/2 HO Scale" trains, but only lists the Baldwin Switcher. These primitive models were ultimately dropped in the late 1960s when Arnold started upgrading their entire line of N scale locomotives.
I've been told that Arnold may have also made (or at least planned) another F unit that predates this one (supposedly an F3). However, since I've never actually seen one I can neither confirm nor deny that such a thing ever existed. I have also come across various referances to F9 B units, but have never actually seen an example of one and am not convinced that they existed either (my guess being that these are simply references to unpowered A units).
The easy way to distinguish these F units from Arnold's later (and vastly superior) FP9 is by their flat and featureless truck sideframes. Additionally, the F9 has a die-cast metal shell (as opposed to the FP9, which has a plastic shell). Up until about 1964, these models came equipped with simple bent-hook couplers. After that, they came equipped with the now familiar "Rapido" style coupler. As pictured above, early versions of the Rapido coupler had long vertical extensions (for backwards compatibility with the earlier bent hook couplers).
At this stage of the game these locomotives are obviously only good as collector's items and wall-shelf babies. The looks border on toyishness and the performance is laughable. They are ridiculously fast (I think mine tops out at about warp factor 9). Pickup is very iffy, what with each truck only picking up one rail. There are only two driving axles and the huge flanges make for some impressive wheelies over turnouts. Still, like Rapido's other early models, these locomotives are an important piece of N scale history.
Trivia - this same basic chassis/mechanism was used for all of Arnold's early diesels and electrics (Baldwin Switcher, V200, and Re 4/4) -
To remove the shell, unscrew the two screws hidden underneath the trucks (one one either end). The shell should lift right off at that point.
(Thanks for the photos, Alex)