a lot of the EGO connectors use brass fittings to cut down on cost. Look at the fittings themselves, and if they have that brownish color, chances are that's what you have. I think most EGOs have that type of connector. It is extremely easy to crossthread it, and if you have enough leverage when you tighten it, you might not even know you're crossthreading.
As far as the EGO to EGO adapter, you might want to look for an EGO airflow adapter. not only does it have an EGO to EGO threading, but it also allows for you to increase or decrease the airflow. Here's a link to one from Madvapes:
eGo Battery Airflow Controller
If you want some inexpensive batteries and are willing to wait a month, Give Fasttech a try. I ordered an 1100Mah VV ego for under $12. It's a good backup battery or an on the road battery. If it breaks.. no worries, it's only $12.
https://www.fasttech.com/products/1408806