The calculator itself is allowed. However, the proctors are often not familiar with CFA at all so there may be a risk that they may be unsure on the day. I’m not sure how good their training / guides are on this.
I’m betting if it says BA II Plus on the top no one will say anything, as that’s all the CFA policy states. I’ve seen quite a variety of styles of that calculator (See below). The one on the right of the first image is the one we use in our CFA BA II Calculator Guide Video, but all have the same buttons.