First of all, if you're selling 10 items per month out of about 80 listings (like you have now), that's a 10-12% sell through rate. IMO that's not bad for a small store.
I have around 6800 items listed and I do specialize. But I don't have that kind of sell through rate. (I wish!)
You mentioned train stuff sells well (which doesn't surprise me). I'd think that a "hodge-podge" seller (as you called it) offering a wide variety of items would naturally begin to specialize in certain areas as it became clear what does and does not sell. Especially if you have a good source of the in-demand stuff. I've seen many seller shere who have completely changed what they sell, since their store names (and sometimes terms and conditions) refer to one type of item, but all their listing are something else.
Some buyers gravitate towards sellers who appear to specialize in their item of interest, because they assume the seller is knowledgeable about the item. This gives them confidence that the seller is describing the item correctly and fairly. This is my business model and the result is that I have a number of regular customers who come and purchase on a regular basis.
There have been times where (as a buyer) I passed on an item because it looked like the seller just picked up random stuff at yard sales, and probably didn't really know much about the item.
On the other hand, offering a variety of items casts a wide net, so you have a much larger pool of potential buyers than someone like myself who specializes. It's probably harder to build a base of regular customers though.
So, is there a right answer to variety vs specialization? Probably not, it's just a matter of the pros and cons of each and what you can make work for you.
But even more important than what sells is, what brings the greatest return? I see a few of your items selling for $1.50, which doesn't provide much profit, even if you got them for free.
If you are a hobby seller, and really don't care how much you bring in, you just enjoy selling stuff, then the return may not be an important factor. I've been here over 22 years, and early on, that would have described a large number of sellers.
But, if the dollars are important, the prior statement holds. How much do you have left after purchasing the item, paying eBay/PayPal fees (on both the item price and shipping) plus packaging materials? And how much time did you invest sourcing the item, listing it and packing it?
If you made the entire $1.50 as profit on the aforementioned item (after all costs), and only invested 10 minutes total to source, list and pack, you are making $9.00/hr. If that is in line with your expectations, good, if not, maybe items with higher returns are in order.
