Generally the panel battery isn’t supplied with the panel, the battery should be sized according to the number of powered detectors etc. typically would be anything in the range of 1.2 - 7.0 Ah.
An installer would normally supply a battery with an alarm system.
If buying one from a retailer or distributor they may sell a kit with one in, but not necessarily the right size for the equipment you intend to use.
There are many different sizes (capacity) and voltages of batteries for alarm systems.
For example a CP40 doesn’t use a lead acid battery, but a NiMH, of a certain voltage and capacity, the cells that make the battery pack are usually wrapped in green.
An Agility 2/3 etc uses a 6V lead acid battery.
Some use 9V batteries and so on. Think Yale and response do, but would have to check to be certain.
Other panels use other batteries, typically the most common being lead acid 12V of various capacities.
In the case of this panel, the battery fitted isn’t what the manufacture recommends as suitable, whether it was provided by the original installer or cobbled together at a service visit or done by an end user isn’t clear, these panels haven’t been available new for some time now.