I assume that the machine was manufactured in the USA, and has a 46 on both sides on the front of the machine? That is where the model number normally appears, but to be honest I've never heard of a Model 46. 

If I had to guess, I'd say that 46 was a number used for export machines and that your typewriter is just a derivative of one of the typical Underwood Standard models, most likely a number 5 with a Danish keyboard. Based on this the serial number suggests that it's a 1922 model. It definitely isnt' a Model 3 as those machines had extra wide carriages. 

You can narrow it down to an exact model using these specs:

Model 4 (J) - Base standard
Model 4 (L) - Base standard with automatic ribbon reverse
Model 4 (P) - Base standard with automatic ribbon reverse, back space key, and ribbon colour selector
Model 4 (D) - Same as 4 (P), but has a paper guide

Model 5 (F) - Same as the 4 (J), but has 4 additional keys (types 84 instead of 76 characters)
Model 5 (R) - Same as 5 (F), but has an automatic ribbon reverse
Model 5 (M) - Same as 5 (R), but has a back space key and a ribbon colour selector
Model 5 (E) - Same as 5 (M), but has a paper guide

Although it's a little hard to tell from your photo, it appears that you have a 1922 Model 5 (E).

Are you aware that you've been creating posts in a large number of very old threads? This thread, for example, is over two years old. Given that the person who created this thread has only five posts to his name, and hasn't replied to this thread since he started it in December, 2013, it's not very likely that he's going to read your comments.

Also worth bringing to your attention is that Typewriter Talk is an international forum. Not every member here has updated their profile to show their geographic location, so you often won't know where the person you're addressing lives, and consequently one shouldn't assume things such as "Ames" being a "very familiar name in the business." This also holds true when discussing product brand names and brick 'n' mortar retailers that might only be well known to those local to you, or the country you live in.   

To the Moderator:  Please cancel my password, as  I do not intend to visit this site ever again.  I have offended and will not do so in the future.  I am going back to my own world and enjoy my hobby privately as I have always done.  Again, my apologies.

No, no! Please don't do that! It'd be a shame to have someone of such knowledge of the typewriter to just pick up and leave because of a mistake like this. We make mistakes all of the time, and I'm sure that's alright with Uwe. With over 1000 machines under your belt, the next step up would be a full time repairman, and it would be such a pity to have your experience and wisdom kept from the wider world of this forum. You've been at it for 35+ years, and it gives me hope that perhaps I will one day make it to that long with my typewriters or even longer. 

For the record, no one has made any mistakes. And my previous post was not meant to chastise, but rather to inform. Those not familiar with online forums often overlook some of the more nuanced aspects of them, which is why on occasion I will bring attention to a few of this forum's features. To wit, many new forum users often don't realize how old a thread is when they reply to it, or assume, because the exchanges are in their native language, that the forum's geographical reach is limited to their corner of the world.

Finally, if anyone wishes to close their membership here they need only send me a PM. I will of course respect their request and close the account; however, all posts that they have contributed will, for the sake of the continuity and thread legibility, remain.